Dan,I have been in the tire business for 15 years.
Not much out there in RWL and nothing comes close to the Polyglas.
The BFG Radial T/A is the closest thing to it as of right now in a radial.But they are now in limited sizes and some are already discontinued and stocks depleted.
Goodyear Eagle GT II and Dunlop Qualifier GT are the next best thing.
Goodyear also owns and manufactures Kelly Charger tires in RWL.
Hercules has the HP4000
But if you prefer the font size and style of the Polyglas,get repops.
Check with Diamond Back Tires to see if they can custom make a set for you.They do specialize in radials that "look" like bias ply tires.But no RWL,though.
However,a double pinstripe whitewall was period correct on a '70 Fusey.
http://www.fuselage.de/index.htmlI know it is not what came on your car originally,but it can pull it off.
Check out their online catalogue:
http://www.dbtires.com/index.htmAlso I do have a really good friend who may still have a set of vintage (circa late 70's/early 80's) belted BFG's.PM and I can pass on the info,if you wish.He pulled them off a set of vintage Western Wheels and installed the wheels on his Polara.