My 93 GMC has a 350 with 4l60E I wanted to use it for pulling our 5th wheel trailer. It has 280K on it. It pulled it good on flat ground but a hill was a real experience. from 55 down to around 30 on a good day. SO I talked to a couple guys and what I wound up with was a set of 305 heads ( had to be right numbers) thy opened them up to 202s added RV cam now were talking. It pulls like I wanted it to .. Just a note that was on the second rebuild the first one I got a set of 305 head gaskets by mistake They don't work on 350s. it has the Performer intake with the adapter for TBI. It pulls that 30 foot trailer all over the place. BUT its more trailer than the truck can handle I think.