I had a set of 78' t-tops from a Regal, 78' is the only year with the outer silver trim I am fairly certain. I test fit them on my 87' for someone who wanted to buy them, had to remove the outer edge trim which was a minor pain. The glass does have little indents in the middle with this trim off, when you see the center bar on the 78's (I was thinking through 80') there are little tabs that help or are supposed to help keep them in place. But without the other trim they fit.
BUICK 1987 Buick GN t-tops
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There was a "1st Design" which encompassed 78 and early 79s, as to which VIN break I am uncertain. And the later 79 "2nd Design". Sure, they likely fit. But the first design is a slight bit smaller according to GM's information. They still likely seal because the T-top seals are fairly wide and the smaller size is probably minscule.
The 1st design for 78 and early 79, the p/n is the same between Regal and Olds with 20104646/4647. The 2nd design for 79 Regal and Olds was (20113990/3991). The 3990/3991 was superseded to 20279512/79513 in Sept. 82, then to 20359056/9057 in Sept. 85.
When that change occurred in 79 to the 2nd design could be 1 month in or 6 months in, or....??? Nobody knows. It's similar to the small horn button to larger horn button switch on the 84 Cutlass that 84 W40 and I were trying to determine. It's guesstimated the early 84 sport steering wheels on Cutlass used the small horn button until sometime either in VERY LATE Decemeber '83 or early part of January '84. Then they went to the silver ring horn button which was larger. We've already determined that there was about 2 or 2 1/2 weeks or so into 84 H/O production that early 84 H/Os were built with a 1 groove PS pulley and single alternator belt like the regular LV2. Somewhere in mid-December '83, the dual belt pulley setup started showing up on the VIN 9 engines. I know for a fact my car, #19, came with the single pulley setup (build week 11E, converted 12/1/83).
So where that VIN break is for the 2nd Design T-tops for 79 is anyone's guess at the moment. Additionally, I believe the early T-top versions (up through 1980 maybe??) had a different "center bar" in the T-top structure, IIRC.
I forgot to mention that in the parts book there is even ANOTHER part number in the T-top glass department that was late 84 to early 85, then a change sometime in 1985 into 1986. I don't know what the difference is for the glass. Perhaps PPG then LOF, or vice-versa, manufacturers? I don't know. Then after the 1st part of 86 with channels, they got rid of the channels leaving yet again a new glass p/n for the 2nd part of 86. This stayed this way until the end of the 88 RWD Cutlass model run.
Those plastic channels appear to be held on with a thin strip of butyl. Not sure, but that's what it looks like to me. Totally understandable that the plastic channels were dropped because of a performance feature causing complaints. They didn't quite meet up properly at the corners and that little gap would catch the T-top bag fibers if you weren't careful. The little corner ends can be pretty sharp. If you were careful, you likely wouldn't chomp up the T-top bags too badly. Kind of a PITA. The plastic channels also would crack and pieces go missing here and there. I was extremely lucky to find a complete set of new ones. Those are some ultra-rare pieces.
Here's info from the Buick parts catalog, May-81.
The 1st design for 78 and early 79, the p/n is the same between Regal and Olds with 20104646/4647. The 2nd design for 79 Regal and Olds was (20113990/3991). The 3990/3991 was superseded to 20279512/79513 in Sept. 82, then to 20359056/9057 in Sept. 85.
When that change occurred in 79 to the 2nd design could be 1 month in or 6 months in, or....??? Nobody knows. It's similar to the small horn button to larger horn button switch on the 84 Cutlass that 84 W40 and I were trying to determine. It's guesstimated the early 84 sport steering wheels on Cutlass used the small horn button until sometime either in VERY LATE Decemeber '83 or early part of January '84. Then they went to the silver ring horn button which was larger. We've already determined that there was about 2 or 2 1/2 weeks or so into 84 H/O production that early 84 H/Os were built with a 1 groove PS pulley and single alternator belt like the regular LV2. Somewhere in mid-December '83, the dual belt pulley setup started showing up on the VIN 9 engines. I know for a fact my car, #19, came with the single pulley setup (build week 11E, converted 12/1/83).
So where that VIN break is for the 2nd Design T-tops for 79 is anyone's guess at the moment. Additionally, I believe the early T-top versions (up through 1980 maybe??) had a different "center bar" in the T-top structure, IIRC.
I forgot to mention that in the parts book there is even ANOTHER part number in the T-top glass department that was late 84 to early 85, then a change sometime in 1985 into 1986. I don't know what the difference is for the glass. Perhaps PPG then LOF, or vice-versa, manufacturers? I don't know. Then after the 1st part of 86 with channels, they got rid of the channels leaving yet again a new glass p/n for the 2nd part of 86. This stayed this way until the end of the 88 RWD Cutlass model run.
Those plastic channels appear to be held on with a thin strip of butyl. Not sure, but that's what it looks like to me. Totally understandable that the plastic channels were dropped because of a performance feature causing complaints. They didn't quite meet up properly at the corners and that little gap would catch the T-top bag fibers if you weren't careful. The little corner ends can be pretty sharp. If you were careful, you likely wouldn't chomp up the T-top bags too badly. Kind of a PITA. The plastic channels also would crack and pieces go missing here and there. I was extremely lucky to find a complete set of new ones. Those are some ultra-rare pieces.
Here's info from the Buick parts catalog, May-81.
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