TH350 to 700R4 Mount Location

[LT1B-Body]

Hello,
I'm going from a TH350 to a 700R4 in a 78' Malibu and using the stock crossmember. I measured both and the 700R4 is 1" longer If this is correct, I should be able to drill a hole one inch down closer to the tubing.
Does this sound right?

 

[78Delta88]

About 3/4 is closer. There is actually and adapter plate you can use.

I've done several of these swaps ... 2004r ---> 700R4 ---> TH350, etc...

 

[78Delta88]

This is the chart

 

[78Delta88]

Been a few years but thinking back to a customer's 78 El Camino. It had a 78 frame with 87 body mounted on it. Frame was powder coated. I put a 700R in it. I think I moved cross member back and drilled frame. But been a while. Moving the cross member doesn't always work, if it will, it is a possibility.

 

[stew86MCSS396]

About 3/4 is closer. There is actually and adapter plate you can use.

I've done several of these swaps ... 2004r ---> 700R4 ---> TH350, etc...

I haven't but I sure brow beat it to death!!! I based my logic on...according to the chart you posted, dimension "C" between the 2 is 22 1/2" vs 20 3/8" a difference of 2 1/8". The distance between the frame bolt holes is approximately 2 1/2". You could possibly slide the crossmember back 1 set of holes and be at 2 1/2" vs 2 1/8". Lengthen the slot if required and drill additional hole/s if deemed necessary. I believe the driver side rail won't have anything to drill if we're talking '83 pre 200-4R frames. I think I would have tried this if I didn't have a 2000 4L60E which dimension "c" is further back.
...and someone will chime in shortly and say it can be done using 3 of the 4 bolt holes cm mounted at an angle...

 

[timo22]

When I put a 700 in my 81 Malibu,(20 yrs. ago) I remember just cutting the crossmember mount pad down and drilling a new hole. Bolted the crossmember in with four bolts in the factory frame holes.

timo22

 

[stew86MCSS396]

lol I tend to over think things and I don't doubt that it is that simple, there is enough room on the tab to make another hole ~2 1/8" back. Keep in mind that the cm goes across the frame rails diagonally, so use the elongated notched hole as your reference not the edge of the tab.