I would stay with "Thrift master" or close to it.
Maybe "Thrift master 350" or "350 Thrift master"
Also, how about the original "Thrift master" with a "350" under it.
You're right. Maybe the later 235 Thriftmaster script...just subbing 350 in the same font.
Never seen this done to a SBC or even thought about it. I'm fairly allergic to V8 conversions, but I'm guessing this will look really cool.
Carl, are you painting it stovebolt gray?