Couple very important things to know about that adapter:
1) If you're running a 59A style cam, you'll probably find that when you put the stock bolts into this adapter, that they might hit the timing cover. When this happens a bunch of metal gets ground off and thrown down into the oil. You may need to modify the adapter to use different fasteners with countersunk heads on them. Something like this:
https://www.mcmaster.com/products/sc...head-screws-9/
2) IMPORTANT: Stock 49-53 cams had an oil-pressure port/hole in the front bearing journal - that fed positive oil pressure to the front of the snout of the cam. The front surface of the cam is a "thrust surface" - if you don't provide a reliable amount of oil-pressure, then it will gall over time. Again - more metal filings in your oil and a cam that is now walking back and forth.
a) CAM: You need to look at a 49-53 CAM, see what was done with the pressurized oil port and replicate it with your 59x type cam. It can't be done with the cam in the engine! You have to drill the cam in two places ---> one in the journal and another through the front of it to hit the journal oil hole.
b) Adapter: It needs to be drilled to allow pressurized oil to reach the front thrust surface. You also want to make sure there is a good fitment on the backside of it (such that you don't have a big pressure leak between the 59X cam front surface and the back of the adapter.
The above usually requires some machine tools (mill, lathe, etc) and knowledge to get it right. If it is not right, then you'll most likely cause damage to the engine.
It is a SHAME that folks like Speedway sell products like this without instructions and warnings like the above.
Best of luck!
B&S