318 magnum will work, though I would want the block milled or new pistons for quench. Not sure how far 318 mag pistons sit in the hole but I'm betting it's past quench depth. 9:1 compression, reuse the stock cam/valvetrain, magnum manifolds or headers, LA spreadbore intake redrilled for magnum heads. I would get something in aluminum but similar to a stock intake, like a performer intake. A wideband o2 sensor would be a definite asset for tuning.

Do you have the 5-speed yet? Sounds to me like that 5-sp stick would set you back some decent coin. If the budget dictates, I guess you could go with a 904 with a 2.76 gear, or build it like a diplomat with a 2.21 gear or a A500 trans with something like a 3.55 gear.