I swapped a bench from a early 80's chevy truck into my blazer using a 88 truck bench seat bracket.
The truck floor was very similar to the blazer, all I had to do was cut a 2 inch or 3 ( can't remember) to shorten the width so the tracks lined up with the bench seat holes and then I took square plates and drilled the holes to match
Took half a day to make it work, plus it utilized the cable and lever of the 88 brackets so the seat still moved way forward since it was out of a extended cab.
Or a popular seat choice is the 60/40/60 seats out of 99-07 chevy trucks. Extremely comfortable and can be fitted easy.
Finding manual sliding seats that are not wore out are hard though since you find them in work trucks mostly but wiring up the driver seat for power isn't that hard and there are plenty of LS packaged Chevys out there that are wrecked with nice seats