I wanted the same thing for my 94 GMC K1500 Sierra and could not find any after extensive search. I ended up buying Rear Whell Well Liners 1999-2006 SKU: 4299 from Rough Country Sales (cost of $89.95). Took a chance and after trimming them a little they fit. It isn't 100% perfect but nobody...
I installed long headers on my 94 GMC K1500 with 5.7l. Bought them from Summit Racing
https://www.summitracing.com/parts/PTE-H8059-1
I have 6 inch lift kit and have true dual magnaflow exhaust with cats. Had no issue fitting the long headers. Works and sounds great.
I did a soundsystem in my 1994 GMC K1500 extended cab truck about 2 years ago and also wanted a subwoofer under rear seat. The perfect fit was a Kenwood Excelon ( https://www.crutchfield.com/p_113PXW804B/Kenwood-Excelon-P-XW804B.html?omnews=9698432 ). I installed a Kicker subwoofer mono 300W...
I wired an LED light strip at top of hood connected to a toggle switch mounted to 12V terminal cover. Truck also has the 30 ft wind up light next to battery.
I'm the original owner of my 94 k1500 with 250000 miles. Pretty much refurbished it and added 6 inch lift kit. Last project was redoing interior which was gutted, dynamat soundproufed with killer sound system. Currently changing out 6 body mounts which I suppose should be changed after 250000...