The 84-87 turbo Buick turbo engines all used a rubber oil pan gasket, no cork (grey in color). I'm not a fan of HV oil pumps. The extra volume puts additional load on the cam drive gear and cam sensor gear. I have seen (and repaired) blocks where the cam wears into the block. If you Blueprint the stock front cover and oil pump, you will pickup oil pressure and get better oil supply without higher loads of a HV cover. It is very important to control oil pump gear end play. I shoot for .003-.004" end play. Do a search. the subject has been beat to death on this forum.
Add the cam roller thrust button. They were manufactured with a plastic cup and spring to control cam thrust. The thrust bearing upgrade is detailed in a Buick Technical Service Bulletin.
Disassemble, clean and inspect your cam sensor. I've seen lots of loose bushings in the cam sensor. Inspect the crankshaft front pulley closely. I've seen plenty that were cracked in the keyway.
New springs, sprockets and chain, valve stem seals.