From what I am reading in a few other forums a replacement cap is probably your best bet.

"Find yourself some main caps, a good shop like mentioned above, probably has a box with caps they have removed from destroyed blocks, foolish if they toss them with the block. It doesnt take very long to try each cap on your block and see which one fits with the best register, and the closest fiting main alignment and parting lines. Any good machinist has or can make the rounded tip tool to improve the register. Once a cap has been found that fits well, and the alignment of the main housing bores are close, we get ready for the align honong process. I dont have to go into the align hone procedure here, but see how simply and inexpensively you can save this block. Align hone with cutting all the main caps should be around or under $200. I bet if you ask here on the HAMB, you can find a couple of used main caps that folks will give you for the shipping cost alone. This is a 100% correct way to save the block. TR "

http://www.jalopyjournal.com/forum/...4aad49274&p=6601741&postcount=20

If the cost is still about $200 that would be smarter/cheaper than finding a new block, cleaning/fluxing and using it.

I would do this before I welded up the web of a highly stressed part (the studs and the caps are the only thing keeping that 80bl crank spinning at 2000RPM in place.