--I don't believe that '61 88s came with 16" wheels.
--Radial tires with inner tubes will require radial-compatible inner tubes or the tubes will fail.
--The wheel centers might be riveted to the outer rims, but they sure aren't pop riveted.
--Different rim part numbers are tube-type rims, others are tubeless-type. Easy to google once you have found the p/n.
--Tube-type rims can often be used with tubeless tires. If they don't leak, then they're fine. My spare is a radial tire on a tube-type 16" rim and it hasn't lost 1psi in the year that it's been there. You never know till you try them.
--Mark
1973 SIII 109 RHD 2.5NA Diesel
0-54mph in just under 11.5 minutes
(9.7 minutes now that she's a 3-door).