I like the Ford 7610 platform and try real hard to keep my 'work string' something similar. Right now on the farm
1- 7610 with cab and loader
1- 7610 orchard
1- 7610 cab loader and 4 wd
1- TB 110 which is based on the same platform
1- 5600, the no turbo little brother.
Keeping like tractors makes keeping more parts on hand worthwhile. It was nice when I bought the 7610 4wd this winter with a bad alternator to pull one already made up and ready to go off the shelf. I try to keep clutches, starters, alternators, water pumps, etc ready to 'plug and play'.