I am not sure I fully understand your problem Jeff , I think it sounds like you have been talking to someone about your tyre needs , but they really didn't know either .
Yes you can fit radials to your original rims and use tubes with them . It is best if you fit radial tubes ,, but the originals will work ok for a long time .
Check out another tyre supplier.
I have the 15" rims on my '40 , which are 5 1/2 " wide , and I have 700R15 light truck radials fitted ,these perform well.
The tyres I have are Dunlop Steelmaster , these come in a range of sizes . There are other makes , like Hankook who also do the light truck range .
Check the link to my truck pic to see how tall they are
.
I have some friends who take their 'off roading' seriously , you should see the weird and oversize tyres they fit onto skinny rims , they work really well , stay on and don't overload the rims . eg , 33 x 12 x 15 on a 7" rim . It does work .
So what I'm saying is ,, if you find a 700R16 tyre , it ought to work ok on your 4"rim , but fit it up and have a look see ,, then see what you think . Test drive it around the block if your tyre shop is friendly .
