Well for starters, you'll need to change your pistons. The compression of the 1968 429 is about 10.5:1, and for a blower you should have closer to 8:1 compression ratio. Further, the stock pistons are cast aluminum and they should be replaced with forged pistons. If you put a blower on the engine without making this modification, I think it will last only about 2 minutes.

While you have the shortblock disassembled, you may as well upgrade your connecting rods too. A high volume oil pump would be a good idea.

Paul