rear end ID

Hi guys,
I recently bought a 64' shorty window Econo ,( and traded a paint job for a 65' Chevy Panel ). I'm kinda working on them both..
I drug myself under the Econo to see what kind of rear end I have and it appears to be a 9" !! Feel pretty lucky if it works and is in good shape. I am putting a 302/ C4 I have sitting around the shop in it... I ID's it as:
WCR - R1
3 . 5 0 7ED 786

I'm assuming the gears are 3.50 (which would be awesome I think with the 302!!) but does anyone know the other #'s to ID it???
Thanks!!!

unless the C4 has the short stock Econoline tail housing it won't fit.

I have another donor C4 that has a really short shaft. May have to swap tails and hope for the best.... I gotta plasma cutter and welder too, for improvisation