Hardcsh, I have had three different barrel sets fit to my MX-2000 receiver. None were a problem, because the receiver is the newer type with 6 digits in the serial number. I'm told 6 digits is the key; however, I only have experience with serial numbers for receivers and barrels higher than 126000.
I bought an O/U barrel set from Giacomo and he fit them to my receiver on the spot. He had to file a touch off of the forearm lug and off the ejector rods to time them. Everything else was perfect.
Later, I bought a used MX-10RS and decided to fit those barrels to my existing receiver. The fit was perfect. Even the forearm lug was the correct length for my forearm. The only thing off was the ejector timing. I took the ejector rods from the MX-10RS and put them in my receiver. Perfect timing.
If your receiver is the newer type, it is unlikely you will have to spend a lot of money to have the barrels fit.