The cost of a 350 HO (true 350 block code and 65 cc #48 350 HO heads) will be high as well as the cost of building a 350. Machining costs will be the same, pistons, rings will be a little more expensive.
The more cost effective solution is a 400 with 77-82 cc heads or 72 cc heads. If use 72 cc heads, Speed Pro/TRW has a piston that will keep your CR to around 9.1-9.6.
If you go the 350 HO route..find a 350 block that has the cylinder walls chamfered for valve clearance. Find a pair of 670 Pontiac heads. Use the 068 cam grind (or Comp Cams regrind)
What would be cool? a 350 HO with the 670 heads (which incidentally are the best low lift head and the only closed chamber Pontiac head) with fuel injection.
That would be interesting.
If time isn't a factor, you could easily search Craigslist and the boards for a block, pistons...etc and come under budget.
One piece of advice? Spend the money up front for the block parts and machining. Get the best bearings, rods, pistons and rings. That mentality will "bulletproof" your bottom end..After that, you have the flexibility to tinker with exhaust, heads, intakes...etc. IMO, the block and prep is paramount.
