60-degree V6?

[GTRS Fiero]

The 3.8 / 3800 has gone through some major changes over the years. I wouldn't count on anything from "Grand National" vintage being able to be used in a Fiero.
Wikipedia has a really detailed dissertation on the GM 3800, including all(?) the changes. I'll post a link later on. I'm at work now. Need to be busy.

I used to have a Fiero with what I was later told was the GN engine.  That Fiero was fast.  Apparently, around 1990, Buick was pulling out of NASCAR, and Buick built an engine to outdo themselves.  I believe it was a turbo V6.  Whatever the engine, it was in a Fiero, and that Fiero was a handful.  The buyer told me a bit about the engine.  I couldn't afford that car, and sold it quickly.  I remember almost nothing about the car, other than that it cost about $5K more than I had to spend.

[Raydar]

I guess the question was what trans pattern the block had.
If it was the GM Metric pattern, it would have bolted to the Fiero trans with no issues. If it had the B-O-P pattern (as I always suspected the Grand National did) then it would have required an adapter plate. Regardless... if it was anything like the GN engine, it was insanely fast.

[GTRS Fiero]

Like I said, a handful.  Had I known more about Fieros, and what I had, I'd have increased the selling price.  At the time, I needed to get my money back out of it.  Honestly, I only did a precursory inspection.  I made sure there was minimal rust, everything worked and seemed sound, and it drove well.  I knew less about Fieros 5 years ago than the little I know now.  I did know the engine wasn't stock.  That's why I'm documenting so carefully with my current Fiero.