'91 was the first year for a 4L80E. A "V" series 1 ton that year could have had a 4L80E/205 so there was a factory adapter - it's discontinued now.
I assume a Suburban that year would have had a 4L80E/241. Since the 241 and 208 are very similar I imagine the 208 would fit using a 208 adapter. (just a guess)
Not sure what difference there are between the 91 and 00 tranny's are though. I'm sure there are tailshaft differences at the very least.