Chevrolet Repair: chevy 350 motors, chevy 350 motors, gmc suburban

Question
I have a 1972 GMC Suburban with what I assume is a 350 motor, I know its not a big block but it is stronger than any of the six others I have had by far.I do not know how many miles are on the motor, nor what other internal modifications may have been made.Accel HEI and Edelbrock manifold and carburetor, air conditioned. Here's the rub. In the past we have had cooling problems, unable to find the source of the problem, finally replaced the radiator and were able to keep it down to about 210 with a 190 thermostat and electric fans.One day on my way home I ran over a towel or something and it threw all three belts, although I did not realize it until I got of the freeway. The temp gauge was pegged, but other than a little noise which was partly because of a bad exhaust donut, there appeared to be no damage. The noise quieted down after exhaust repair, but you could still hear it in the background. I originally thought valve.Yesterday, after about two months of driving 250 miles/week, I went under the hood to check the fluids and noticed what appears to be oil in the coolant, which was not there three days before. There does not appear to be coolant in the oil. One mechanic who used to rebuild 10-12 engines per month says probably cracked block, another mechanic says he has never seen a cracked 350 block in California, probably a cracked head.About a $2000 difference in the solution. Your thoughts?

Answer
Hi Tony, If there is OIL in the coolant it had to come from a oil pressure passage which is in the block on this engine, not the head. I have seen cracked blocks where the lifters are! This will put coolant into the radiator.

Sounds like a new engine to me

Have a Great Day    Mark