got it . u were the only one who actually knew the head casting # were under valve covers.
Is the block # underneath? almost has to be cant see any from eng compt.
here is what I found so far
head # 3989241 build date dec 10 71 also has GM 4 T stamped in middle inside.
looked on everything I can find and cannot find that head #.
intake man # is 6263753
here is what I found under valve covers today.
motor ran like crap. did comp test. # 4-6-5 low at 25 lbs.
on same cyl intake rockers were sideways and push rods bent. exhaust look ok. will have to pull head to look at piston tops , and also get pieces of pushrods, maybe bent valves. don't have any idea what caused this. the heads are clean and look like new under valve covers. going to crawl under to look for block #
thanks again