Yes, they can as long as both are the same on each axle.
You can substitute these tries if need be. But if you do this your car will be off balance.
Yes, that is a pretty good substitute.
Normally. yes.
Yes, you can
Normally, yes. The 65 tire is slightly shorter that the 70. A much better swap would be to go with a 225/65-15.
no there is too much height difference
It is an acceptable substitute, but know that your speedometer will read 58.7 at a true 60 mph.
Yes, that is reasonable as long as both sides match.
Yes, if you mount as a pair. Both tires on axle must be the same
Possibly, check they don't rub anywhere while steering.
215/70/r15, 215/75/r15, 225/70/r15. I think that some may have also came with 14inch wheels. I have put tires as large as 225/75/r15 or as small as 205/75/r15 on an 84 without any issues.
215 65 r 15 or 205 60 r 15