A question for the Regal folks, even though it is not a v8. What casting numbers will work for an 86 T-type. Looking for a new block, may have found one, not sure if matters with the 20bolt?
Buick V6 Casting Numbers Refer to: The Turbo Regal Web Site, www.gnttype.org. This site will provide Buick V6 casting numbers.
the short version: 85 and up should be 20 bolt. the preferred block number ends in "109", although the 85 will work, but you will need to tap the hole for the turbo drain line.