The owner's manual that was in my '70 Monaco stated that radial tires could be used, but they would basically "ride rougher" than the standard bias-belted tires that came on the cars that model year. I put some Pirelli P76 radials on mine JR78x15 (8.85x15) rather than the stock H78x15 belted tires to raise it up a little bit so the rear factory dual exh pipes did not drag on some driveway approaches. Accounting for the sidewall flex, too. They worked well. The P76s were claimed to be tuned for American car suspensions.
Not sure about 1969, but some 1970 C-body power drum brake cars had "recessed mount" drums. Basically, the finned portion wrapped around the brake shoes, which meant that some wheels would hit the fins before the lug nut area touched the drums. W23s came on my car and seemed to not have that problem, but other wheels might.
IF you like the look of the E-body Rallye Wheels, look for a '76 Charger SE in the salvage yards. They came with a version of that wheel, but in 15x6.5 sizing. The E-bodies used 15x7s, which is what everybody wants, sometimes. The 6.5s probably need a narrower trim ring. The E-body 14" Rallyes were 14x5.5 . Something else that might look good if you can find them is the 15x7 Polycast wheels that came on '76 Cordobas, just get the trim ring and center cap.
Happy Holidays!
CBODY67
