[A1971Blazer]

Also be aware that simply spinning the oil pump with some kind of rod ain't gonna pressurize the oil passages......you need to find an old distributor, gut the rotor and all off of it and grind or machine the teeth off of the gear....
it has a couple of bosses around it that channel the oil in the proper direction to the cam bearings, lifters and main bearings. You can set it down in the hole and engage the pump drive, then spin it with a drill while you hold the outside still.

Otherwise, the oil just pumps up thru the rear main into the back of the cam and lifter galley and runs right back into the pan.....no pressure.

I put a set of lifters in my 350 a couple of months ago....I have an old "primer" that I used.....when I spun it up, it pumped oil all the way up thru the pushrods to the top of the rockers......I guess my oil pump is good.....!