I don't know about cast or not and I thought they changed to the AE models a couple years before but......
The receivers on the '65 to early 80's were definetly what is often refered to as "mystery metal". They were complete crap and rusted bad. They rusted under a plateing and then fell away. It did not change how they functioned in the least. The biggest problem with the post '64 Win 94's "function wise" were the stamped lifters used on post '64 models up to the early 70's. Some lasted only a couple shots, some lasted longer.
Now as far as post '64 quality IMO the early model AE's (angle eject) are pretty good. The biggest issue most shooters have is with the rebounding hammer and the 7-8lbs trigger pull. But it took me less than $20 and 1 hour to get it down to 4 lbs. The fit and finish of the early AE's were pretty good even with the birch wood on the Rangers.