i would find a stock set and have your block align bored/honed. either way your going to have to align bore it....
x2any factory 318/340 caps will work or i use pro gram for billet caps. The block will need to be align bored and honed regardless of stock or aftermarket. You might also want to think about if you need main studs too as the time is now.
Find a nice JunkYard 318 and steal them...same thing....318 wont miss em'
EDIT: looks like you already doing my recommendation.
But then again....if you think a set of magical "340" Main Caps are worth all your stress....by all means
100% correct, this guy is!!Factory 318's use a different main cap than a 340. Although they will work the 340 caps are taller and meatier. I just went through this on my 340.
Milodon also makes main caps for the small block.