The 248 has a shorter stroke... I think 3 13/16 of an inch. The 270 and 302 had a 4 inch stroke. It was popular to put the 248 short stroke crank in the 302s to reduce friction and rev higher. Some torque would be lost, and some upper range performance would be gained.
Putting a 270 crank in a 248 would basically give you a little bit more stroke and increase torque. I'm not sure how many cubic inches you would pick up.
