Following. I have an 81 Malibu wagon with the olds 403 and need to do the same thing.
From everything I came across checking in on the Jegs kit last year it's a Heartthrob kit. All three use the same "test" car pics & instructions for the kits.The Summit kit is made by Heartthrob in Minnesota, so if you are a Made in USA fan, I recommend that kit over Jegs which is 'imported'.
I had the custom 2" duals off my 70S Cutlass with manifolds, off a 260 on my 88 Cutlass. I actually had an all 2.5" custom downpipes into a compact X pipe, in place of the Y pipe, into a Hooker G body cat back system, all through the passenger side hump. It was with Sanderson shorty headers but manifolds have similar placement. I actually have it off in my shop, so I can take pics. I put the 2" duals and manifolds back on the Olds 350 in my 70S. The 2.5" was droning and blah on the 70 Cutlass, sounded amazing on my 88, which is why it is going back on. Plus it made a big difference in the higher rpms on the Olds 260 in my 88 Cutlass. You could try the Ramair Restorations 2.5" downpipes with manifolds, work with A and F bodies. A G body is tighter by the A arms and nearly everywhere else. Good luck.
I got a set of Sanderson headers, a Pypes regal style 2.5" system and tied in the drops. Took a double hump crossmember with a slight modification, elongated the slot for the trans. 82 cutlass with Olds power 200R4 combo. I played at it and still had it in in a day.
Ah. I spoke to the Heartthrob folks about a dual kit for the K10, having bought similar systems via JC Whitney 15-20 years ago. I mentioned the G-body kits, whether they could make me behind-the-wheel tailpipes. The guy laughed and said, WE made those for Summit and Jegs, though Jegs is now getting them overseas.
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