Well,that is quite a question.

If you are going to scope them then you really IMHO need to change the standard Mauser safety. I think that the high mounted scopes although thy look the business historicaly are aqwuard to shoot with (for me anyway) So you will not end up with true Mausers, rather a custom rifle based on a Mauser action. If the actions and stocks of the pre-war (which one ?) that you have are pristine, then you are into a simple rebarrel and some limited action work for the 9.62 and the 404 and if you duplicate the barrel profile, but a bit larger diamiter for the 404 then you can proberbly get away with opening the barrel channel.
If they are a bit rough and are going to need re-stocking, blueing flatting, buffing etc then you are going to get into big bucks pretty quickly.
I am no winchester expert but I don't believe (please somebody correct me if I am wrong) that they were ever built in 9.3 or 404. 7 x 57 I don't know but I don't recall that either. So again you are into custom rifles.
Given the price of pre 64 Winchesters then I think that selling your mausers may not raise enough to buy the same number of pre 64's.
The Mausers when modified will have the same bolt throw, because neither the ejector box or the reciever locking lugs will move. If the action of the Winchester is adjusted by moving the bolt stop then the will all have different bolt throws it would seem unless all are altered to be the same as the 404 with some wasted length for the smaller calibers.

The bottom line would be what do you want to spend?

At the London auction that I attended with Pieter and Rigby Mauser in December, you could have bought Cogswell 404 Mausers in neeed of a re-blue and a refinish of the stock for around $3000.00, even allowing for paying somebody like me buying one for you and the paperwork to ship, you are going to get an origional for around $ 4000.00. I would bet that you will spend a lot more getting one built and it is still a shooter that will not apprciate a lot, whilst one of these would proberbly hold its value in real terms.

I don't know if that helps or makes it worse.

Regards