I have seen some ppl make good power with the 305. But have you also called the local junk yards to see how much a LS motor would be with harness and cam. The larger bores can easily make 400 hp/tq 350 gen I or II will struggle to make the numbers for the mpg and power output. Also some small mods really can make them scream.
Other than that i would recomend a gen I 383. It will make the numbers needed to move a heavy car. Also very little cost over the std bore 350 rebuild. You cna buy a junk yard 350 and have it bored add the simple external balanced stroker kit and go. Also works with parts younhave and wont need different intake and heads. Some good regular heads and your good. Usally the after market rotating assembly is stronger than most stock stuff. Even with pmd rods. The cast cranks are fine for 400 hp range. No need to get forged or internally balanced.