Drive shaft length?

I am planning on swapping out the toploader in my '70 to a T-5z. I have the trans, bellhousing, clutch lever, clutch and pressure plate. I am still gathering up some other parts: hyd clutch kit, crossmember and yoke.

A friend of mine did this swap in his '65 fb and found that the drive shaft from an Explorer was the perfect length and it's alum to boot. I would love to do this as well if it is possible. Can anyone tell me if there is a difference in length between a '65 and '70 driveshalft?

When I do the swap I probably need to replace my flywheel as well. Sometimes when I start the car the starter grinds. The starter was replaced about 2 years ago so I'm thinking a must have a few bad teeth on the flywheel. I know an alum flywheel would save a lot of weight but they are not cheap. Would this make a big enough difference performance wize to pony up the $$ or should I just replace w/ stock?

Thanks in advance for your help!!