Xr5 turbo timing

[chevy527]

Hello everyone
I'm new to the forum:
My son brought a second hand motor with low*km.
Was advised the motor was ok from the person we brought it off!!! Hmm, mm
So we replace his engine (that had a cracked cylinder liner) with the second hand one, but notice after the fact we put it in, that the timing looked out. So I found TDC and noted that the timing marks were not lining up, intake side was TDC and the exhaust was about 3 o'clock. So we took out the spark plugs and check the compression and couldn't get a reading.
Question: What would be the check or step to take?
Is it to put a new timing belt, tensioner and seals and reline timing?
Then do compression test??

Cheers