well mhsred i would bet keeping smallblock would be cheeper due to the heads you have and the bellhousing/mounts that are already setup for the la engine.
you have to try and decide the howfast question that you will be happy with. going low 12s and driving it like a jetta on regular is a lot nicer than a trailer expencive fuel setup.
if you go bigblock i would do a stroker 400 with the 440 crank. those blocks will handle a good bit more power than a LA or 440 or 383 block.
for the anti bigblock guy here the only pisser is the plug changing at times. with engine ears it goes in easy and bell housing bolts are easy also. but then you need a whole pile of spare parts to build from. but on the other hand i was going 10.30s on a stock block stock rod stock crank 440 with the old smaller indy heads on a 262/265@.050 630lift solid cam. you will not do that with a 360 with a stock crank and stock rods. you just need good pistons and good heads.keep it around 630hp and stock will do.

before you buy anything people are unloading stuff like mad. i could of gotten a shortblock that with 440-1s went mid9s for 2500 bucks. look around and take your time.