Definitely check compression.... especially a used motor! I had to junk my first donor motor because of compression. Do the oil breather "dance" check. Because of lack of new parts, specialty tools, motor weight and stock tuning designs of the motor... I would not do my OM617 swap again.
Mine is a gutless wonder in my 95 4runner. I would suggest checking compression. If that’s good start doing bolt on upgrades like injection pump and a turbo. Does yours idle ok?