Are all the parts in 870 interchangeable with all 870's? I picked up a new stripped receiver for almost nothing and have almost enough spare parts to build it but this is a new style receiver with the dimples in the mag tube and all my old parts are from a early 90' gun including a steel trigger assembly. I think all the old parts will work just fine in the new receiver but want to make sure Remington didn't do some spec changes in the new express, also the old style trigger group is very tight in the new reciever and you have to really hammer it in with your hand.