I have found a 700r4 transmission out of a 84 blazer, will i be able to put it in my 87 blazer.the 84 has a 350 motor and also the same np208 transfer case. am i fine or what do i need to look for?

as long as the trans had the same engine size it will fit !!!!

you may want to change the wiring in the trans,, so the converter
will lock properly/// the plug in the case will be different.

the valve body may look different {aux valve body in the back} but
the ports for the switches should still be there!!!

if you cannot get it to lock /// 5/16 check ball in the lu solenoid will
get the same results without the electrical BS