Funny you should ask because I just measured all this on my 69 RR yesterday. The Plymouth will be the same as the Dodge except for the out tub and quarter.

From the rear quarter inside fender lip to lip is 74-1/2"
The tire you're using has a 12"cross section
10" wheel with 5-1/2" backspace + 1" of tire makes a total backspace of 6-1/2" OR 5-1/2" on the front spacing
So 60" axle width plus 11" (for two wheels/tires) = 71"

So you'll have 1-3/4" from the tire wall to the fender lip - probably more because yours is a Dodge

But the problem will be the inside of the tub. The original tubs measure 14" from the lip.
With that wheel tire combo you'll only have 1/4" clearance AT THE MOST from the tub.

A 1/2" wheel spacer will solve your problem but I think you could use a wheel with a 4-1/2" backspace with no problems at all.