Study using the milli volt method in the archives . Sounds like the first cylinders fuel calibration in the injectiion pump may be way off.

You are right in that the timing in of that injection pump would have been hard to find an acceptable place. Doing what I think will need done is important as accuratly as you can as the number one injection element is your pumps drip or lock timing refferance.

By ear is not going to get you close enough I suspect. You want that number one cylinder runing at the same temperature as the other cylinders. So you have all your soldiers lined up. Also have a close look for any paint markings on the number one element adjustment if there.

I just noticed you have the 603 injection pump with the internal but acceptable and accessable adjustments. I would also change the delivery valve seal as well on that number one cylinder before starting to go further. You have to or should use a dial caliper gauge to determine the start of the element adjustment if you have to go that far.

Semi starvation of the number 4 and 5 elements of the last injection pump. Did you ever check for adaquate fuel pressure with the old pump? Or run the old pump on vegatable oil to check for worn elements?