We have done builds of hundreds of turbo Buick engines and never used a HV cover as the stock gears have been proven to do the job very well up to 1000 HP builds, including the one listed in my signature.
TA machines the timing cover to specs better than factory, and that has proven to be the best unit available.
The HV timing cover TA sells is a Silver Seal, and their recent stock was returned as you stated since the specs were WAY out of tolerance.
If you are in a bind, I have a couple new TA covers for builds I am doing, but can divert one to you as our assembly schedule is a couple weeks away, and I can ship it to your shop.