I’m guessing the concern is the narrowness of the bench and very upright back. Most car seats will likely hang off the edge. Probably not a big deal if they are fastened tightly, but using the retractable vehicle belts might not work so great. Go for the center belt that is at least a fixed length.
Are you needing a forward facing child seat or a rear facing infant seat? Are the front seats the 50/50 bench or captain chairs with a console? I know the usual advice is that the back seat is safest, but if I had to carry a rear facing infant car seat in a a Supercab I would probably want a front bench seat with the infant seat in the center with a tightly adjusted lap belt.
If you are talking about a forward facing seat, look for ones that are flat on the bottom. Many of the larger “booster” style seats are rounded and made to nest into the bucket depressions that most vehicles now have. When my son was about 4 years old I had a seat like that in my 1966 F100 with a flat bench seat. No matter how tight I tightened it, the seat would roll to the side when I drove around corners. My son would complain daddy daddy I’m knocking over!!! Some of the Graco seats that I have for my grandkids adjust quite large but don’t have the round bottom and would work much better. I believe we now have six car seats for the live-in grand kids... two each in three vehicles. When I get home on Monday after my work block I will check them out and see if one might look like a better fit than the others for a narrow Supercab bench.
SHORT BED 4-DOOR DIESEL: 1986 F350 4x4 under construction-- 7.3 IDIT ZF5+GVOD
STRAIGHT SIX 4X4: 1981 F150 2wd to 4x4-- 300 I6 close ratio diesel T19, hydroboost brakes, Saginaw steering
BIG F: 1995 F-Superduty under construction— converting to 6.9L IDI diesel ZF5+DNE2