I read the OPs post, had to step back, get another cup of coffee, relax a bit and come back and read it again.
Turn a Model 70 into a Remington M40 version of a M700.
They are two different rifles, both good rifles. That would be akin to saying you want to convert a Model 27 S&W into a Colt Python.
You want a Model 40 get a Remington 700 and make one, you want a Model 70 target rifle buy or build one.
They had Model 70 sniper rifles, in reality they were target rifles. They are well made and accurate. But the cost more to build then the Remington and that's why Remington got the contract to build M24s (Army) and M40s Marines.
The Army Marksmanship Unit was big on Model 70 Target rifles. I have two AMU built Model 70s, (one in 308 and one in 300 WM) that I got from the CMP Auction Site. They also have AMU Model 700s or 40X's (tgt. version) pop up every now and then but I like Model 70s.
Both the Model 70 and 700 are good rifles. I believe the Model 70 has a better trigger, and (a biggie in the target rifles) the Model 70 has a flat receiver as opposed to the round receiver of the Remington. When it comes to bedding a target rifle that is a big advantage.
The main difference between the two is the personal opinions of the shooter.
Same as the difference between ford and chevy.
Model 70 Tgt. in 308.
Model 70 Tgt in 300 WM.
Nothing wrong with wanting a M40 or M24 Clone, but you have to start with a Remington, its a completely different rifle then the Model 70.