If yur starting from zero, a 360 is the way to go.
A 7.25 will go a long way for OP's stated use, as long as it is not peg-legged.
If one was to gear, and cam them both, for the same low-rpm to-the-road torque output, then at 65mph, the 360 will battle well for the fuel economy prize.
That is to say,take something like;
a 252* cammed 318 and 3.23s with 65=2608*,
compared to
a 245* cammed 360 with 2.73s, and 65=2200*
(* = @zero-slip)
But nobody does that, and so, when the 360 drops mpgs compared to their previous 318, oh, the 360 is sooooo hard on gas, they say. Well duh. It also spanks the previous 318.
There is nothing a 318 can do, that a 360 cannot do better.... except perhaps, pull mpgs when each engine is optimized , and saddled with the same final-drive ratio.
But with a little engineering a modified 360 can out mpg a stock 8/1 318 while making way more torque and power. I'll guess ~ 40/50% more torque and ~50/60% more power with ~20/30% more mpgs, than the oem smogger-teen. Heck, one 360combo I built made about double the fuel mileage of the freshened smogger-teen I took out.
Yeah, the execution might cost a bit more than a rebuilt 318, but what price do you put on the SMILES per hour?
