Common regency conversions had aftermarket leather seats, wood dash trim, fiberglass running boards, custom paint and wheels. usually a billet grille etc.
Regency conversions was started as a Van Conversion business for custom vans back in the day but went bankrupt a couple years ago like most conversion companies. its not going to be major stuff but nice stuff. they had different packages on them so theres no way of knowing what was done unless u look at it, then its obvious. they were local to my area so Regency conversions were very popular. (FYI the gold "badge" behind the rear door is just the generic conversion vehicle manufacturers association badge...on all conversion vans and trucks)
here's a couple googled pics of a 06 yukon regency conversion..probally similar to yours....so probally flares, wheels, probally a pinstripe, billet grille and aftermarket leather and molded wood dash trim....usually a DVD player and monitor too..
regency was a good company...did some good trucks and vans. the only real big one left is Explorer vans...they do a nice package on an Express...
and also for more reference, my dad had a 1990 suburban that was a Sherrod Conversion and it had custom paint (lots of stripes that were common in the 90s), leather captains and fold out sofa bed in the back 3rd row section, lots of real wood crap, indirect lighting, TV VCR, fiberglass running boards, grille guard, etc...very typical of a conversion...
the one thing to keep in mind on a conversion....they were shit ass expensive new...(those new Express conversions are common to be priced in the 50-70k range) but they are completely worthless as far as resale...all the book values only go by the truck it started out as....since the conversion is aftermarket equipment and loan value and book values go by MSRP pricing....so, its common to get a nice used conversion for the same price as a base level truck, which most of them were made from since they replaced all the goodies...
post some pics of the bad boy...
also, on the topic of conversions...Unique conversions that was right here where i live, back in 99 i think, did up a neat Suburban SS ....was black, cant remember all the details but i think it had two toned or maybe leather and suede aftermarket seats, carbon fiber trim instead of the usual conversion company wood....slick rims, some ground effects style runnign boards, levelled out suspension, all blacked out, and had the SS from the impala SS emblems back in 94-94 on the rear quarter panels...Chevy alloted like one per dealer i think...they were slick but back in 99 they were like 70 grand MSRP...needless to say they didnt sell too fast...i tried to google one but cant find one right now..but they did make a slick OBS burb