nope, not crazy. I have a mag headed 318 in my 4000lb 5th ave with 3.55's and a 42RH (A500). very fun combo, as fast as an AWD 300C. mine's carbed and modded with a reground cam, eddie air gap, 600 carb, and headers. wish I had EFI on it, I have 2/3 the parts to do it, just not the time.

if you want some more gusto, take the cam, send it out to bullit cams, and have Tim put the HR259/316 lobe on both the intake and exhaust lobe, keeping the stock LCA. then get the hughes engines #1110 springs and their retainers. it'll make a ton more power, but still be mild enough to work with a factory ECU. a stock high stall lockup converter will work great with it.