1992 Isuzu Bighorn possible injector timing out?

I recently did a motor upgrade to my vehicle the motor I brought was out of a 98 bighorn so I had to put my old injector pump onto the new motor so the wiring was the same. While I was in there I installed a new timing belt.
I got crank to tdc locked the injector pump and cam with bolts into the block. Replaced belt removed bolts and rotated the crank 2 full turns and back to tdc. The bolts went straight back into the pump and cam with no adjustment. So in theory the timing is correct.
Now the truck is very hard to start, runs very rough and blows a lot of white smoke, I believe this is due to the injector pump timing being out but I am unsure how to fix. I have been told to undo the three bolts holding injector pump and turn pump slightly until I find correct placement. This seems like a very hit and miss solution.
Can you please help and tell me weather this is a easy fix or if I should push my truck to local diesel mechanic.

Thanx