Yes of course the timing cover flexes, but a stock type water pump housing does an admirable job at stopping it.

Of course this means dinking around for awhile, spending time on it, adding a piece of metal between the two parts that is just the right thickness to take up the space, without killing the clearance.

For a guy working out of the garage at home on a budget, where time is more plentiful than money....when the money spent might mean the difference between buying something more important he should absolutely spend the time dinking around with it and get it right, it will cost him next to nothing and he can set the cam end play wherever the heck he wants.

For a pro where time is money, whatever time you spend checking/correcting anything old is probably more expensive than the most expensive brand new part you could get...so anything old does not make sense from that perspective....in that situation stock timing cover is best used as a frisbee, or (preferably) give it away to one of us guys working at home in the garage.....