Re: Lifter issue with an XY 250
This doesnt answer your question exactly, but I have encountered something similar..
When I was trying to get a set of roller rockers, it turns out I have to run V8 Cleveland lifters in my 6 cylinder block.
Maybe what you have happening is that one set is the "six" length, the other is the "cleveland" length and they just put the wrong ones in the wrong box?
Is it possible one set are hydraulic, while the other ones are solid etc?
I have also noticed with my three six cylinder engines lying around in the shed, I have two different push rod lengths..