No, not really since a stock radiator had no pressure cap. It might run OK in some situations but others it will boil. IMHO if you pressurize it to about 12 to 15lbs that would technically work, but the seams in the tanks would most likely fail under pressure.
sorry to highjack, but is a stock A suitable for a buick 215? or isn't it for the same reasons as above.
Run a search on this and you'll get quite a few hits on this topic. But, I'll save you a little time. The answer is somewhere between "Hell no!" and "I've been running a stocker for a thousand years!" Truth is guys have successfully ran stockers with SBC for years. Assuming it is in good shape, the core is more that adequate for the job. The major problem with a stock "A" radiator is it is not a closed system. You can literaly pump all the water out through the oveflow. There are a couple of tricks to make things better. A good core will take 2lbs pressure without a problem. Get your hands on a 2lb cap and 2lb disc brake residual valve and attach it to the end of the overflow. This will keep things from peculating the water out of the radiator. ...or as you will not doubt hear "Hell no! You gotta buy a (Walker, Mustang, Brassworks etc.) radiator." They are right...all except the "gotta" part. Regarding the 215 Buick/Rover engine and a stock "A" radiator...guess what I'm running?
'31 "A" coupe - 1963 215 Buick warmed over - T5 - Jag rear - stock "A" radiator. I'll see if I can dig up some photos.
http://www.jalopyjournal.com/forum/showthread.php?p=8018891#post8018891 Stock 29 Model A/SBC with a piece of copper tube on the lower hose for passenger side connection. Been driving for about a year & to the last viva LV
I ran a stock radiator ($20 swap meet find)that was recored at some point in time. I had it pressued tested, then had the filler neck closed off and an under hood filler neck added which I ran a 7lb cap on. Ran that for about 20 years on a Buick V-6.