Well, the first MF rolled out in 1957 and shares most of the exact same parts as the Fergusons before, so we are talking about a lot of machines from them to current production. What is he wanting restored?
I would start with your local Facebook page. Try joining
South Texas Used Farm and Ranch Equipment
AND/OR
SOUTH TEXAS FARM & RANCH BUY,SELL,TRADE EQUIPMENT
Ask on there for recommendations near where you are. There are dozens of people that do exactly this for fun. There is some 75 year old man named Bob or Fred and he worked on these when they were new. If you go to Massey Ferguson, you will go broke.
Now, for the unsolicited advice....I have personally worked my tractors … Farmalls, Ford, McCormick, International, Ferguson, Massey Ferguson, and probably a few other brands that aren't all that common. This is going to be a ridiculously expensive undertaking if he is not going to do any of the work himself. These old machines are like onions as you get into them. So....start simple. Replace only that which NEEDS it.
He just needs someone that works on tractors and has the equipment to split a tractor and remove a motor if needed.
Good luck. There are a lot of places online to get parts and just about all are readily available.