I just picked up a 65 C30 it has a stright 6 but not sure which the 65 manual says that if it is green then a 292 well it looks green but would like to find a number on the block to confirm this. Numbers I found are F1120B just above the disreibuter,
CON 2 J 10 3 on the rear of the right side of block
3850817 GM 14 on the center of the right side of block.
On the intake manifold 3859381 GM12 and also on the intake man near the fire wall D195.
There is a number on the head but having some trouble reading it maybe 488381F.
The truck runs well I drove it home about 70 miles body needs the usual patches rockers,cab floor bottom of hood and paint, only complaint is the dash was cut to fit in a modern radio but if I remove the radio it looks like a delete plate will cover it. I will post some photos or a link to some this weekend
Ed