I can help with a couple points - with a 3.38 rear, an overdrive would be useless .... if you're not going to be racing why worry about max hp? any stock 350 will pull a trailer fine and cruise nicely, and for that price you better be getting as good a warranty as for a crate motor from a dealer .... for exhaust, the stock rams horn style work well and fit perfect with no leak worries .... the rad will be fine but because the SB is shorter than the 235 you will definitely need a shroud [350 in 56 panel]

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics