car is HJ-45 -78. it has h-41 transmission.
what kind of problems there will be?
if i change engine will it fit to the transmission and what kind of problems there will be with the clutch release cylinder?
The H to 2H swap is pretty straight forward and common swap. The 2H is the evolutionary motor of the H. Rather like the Volvo B20 is is the evolutionary motor to the B18.(or Saab 2.0 /1835)
There will be some minor differences in regards the inlet and exhaust plumbing, but the basic mechanics of clutch/bellhousing are the same.
You will need the 2H motor to be complete with inlet and exhaust manifolds because they are not directly interchangeable with the H.
If your H motor uses a solenoid instead of an EDIC motor to control the injector pump, then you will need to do some grafting of the electrics to upgrade to the EDIC motor control.