What is Difference between 645 and 645B loaders

In this form, the 645 was manufactured up to 1972 when an upgrade of the design was undertaken.

Principal changes included a new engine, the model 3500-II and the introduction of Allison’s new “soft-shift” modulated transmission.

Bucket capacities and tipping loads remained the same.

Throughout the upheaval of the Fiat buy up, the 645B continued in production (as the Fiat-Allis 645B) and was finally declared obsolete in 1981 after some 6200 had been produced.

The model 645/645B was the most successful and numerous wheel loader ever manufactured by Allis-Chalmers.

As far as hard parts I'd think they are very close and if the donor can be had cheap enough, and you have need, the purchase would be justified with the first part swapped.  

Yes, the company is called Ljungby Maskin. For many years they rebuilt old Allis loaders and then later, (after Allis was all finished so as to not get in trouble with patent laws) they started building new ones. When you check out their design, especially of the loader arms, tilt and cylinder placements they are a true copy of the articulated Allis loaders. They have now gone away from rebuilding Allis loaders and don't supply any such (aftermarket) parts. In the European market, especially, Ljungby loaders are of good reputation, expensive to buy used, even with 20 to 30 thousand hours on the meter.