Engine stops running at about 45 mph
 

We dropped an '80 rx7 engine (5 speed tranny) into an '82 with an automatic trans. The '80 12a ran great before we switched it over. Now, the car runs fine until it hits 45-50 then it just dies.

Any ideas?

a brick wall?

are you sure it isnt a certain rpm that it cuts out on? Try reving it and see if it cuts out at a certain rpm.

maybe 5th gear kills it? i dunno lol