Build the Poly. It's essentially the same block as the LA (with subtle differences) and heads with a valve layout that are much better than an LA. Sure the Poly weighs more, pistons may cost a little more depending on what you want to do for your build and intake manifold options are limited. There are a number of stroker options based on what you're after. Contact Bruce Toth on the east coast or Gary Pavlovich on the west coast for options and parts.

My new poly isn't stroked but I'll be in the neighborhood of 475 HP, running a TKO600 in my 65 Dodge SNB pickup. Sure, that isn't huge by today's standards but respectable for what it is.