Joelvv
Newbie
8 lug, 9.5" SF axles are VERY common. There were a ton of them on the GMT400 trucks. I'd say most 2500 8 lug trucks had them. All 2500 trucks were 8600lb GVWR, regardless of whether they had a SF or FF rear end. They were also used exclusively on GMT800 2500 (non HD) and 1500HD, both of which had an 8600lb GVWR.Not saying you are not right but I have not seen a SF 8-lug rear or atleast it is not common. On the Express vans atleast there were 2 different 2500 models. One had 6 lug wheels, a SF 9.5" and a 4L60E and then there was the 8-lug, FF 10.5" with a 4L80E. Depended on the GVW you choose.
To the OP: The 9.5 is an excellent rear end, and would LIKELY hold up to a 454 towing, but the 10.5 would be better. No difference in the transmissions. All 8 lug trucks have a 4L80E. The only time a 4L80E was different is in the 3500HD. Something else to consider is if you buy a truck with a 454, it should come factory with hydroboost.