legal. not easy. no.
hell, besides the engine you need a completely different crossmember, gearbox, driveshaft, wiring, ecu, diff, power steering, alternator, waterpump, fuel pump, oil pump, intake manifold, exhaust manifold, etc.
which part of going from a 1980's cast iron block engine to a 1990's alloy engine did you think was gonna be easy?
can be done, but given your ghetto budget it's gonna cost you too much compared to the cost of the car.