1964 plymouth valiant recommended rim for 245s in the back

Whatsup guys. Today is a good day. Rear end is installed and brakes also.

I have my measurements. They are as follows: from front of the face of the disc brakes here are the numbers

5 1/4 to lip

6 3/8 to leaf spring

3 1/2 top of inside wheel well

I want to run 245s on the back. What size rim 15 x what ? and what backspacing would allow me to fit a 245 on my rear ?

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