LT1GMC

Building a 502 with 500 EFI cam, Intake, and sidemount Whipple. Thought we had the exhaust covered with older but decent Merc/Gil manifolds and the shorter risers for a silent choice exhaust. A trial fit tonight was disappointing as the Merc/Gil manifolds are alot taller than the stock ones and cannot fit in any way with the sidemount Whipple. I know the CMI units like that came on the 500 EFI will work but are too pricey and we would like something that will work with silent choice. Anyone used EMI Thunders, Stainless Marine, or anything else? We don't want to buy the wrong ones again.
Thanks for any input.