The NPR model series started in 1985.
Before then the models here were called KT26, they had a 3.9L engine which may or may not have been a 4BD1.
There was an earlier engine the 4BB1, but I can't find any information on it. We have a hitachi excavator here with a 6BB1 though.
My 4BD1T is from a 1986 NPR, truck model NPR59. Engine model number are cast into the block (beside the starter) and also in the head.
The non turbo 4BD1 has different pistons (approx 6mm taller), no oil squirters to cool the pistons and no aneroid on the back of the fuel pump.
The block has no oil drain hole on the exhaust side and no oil cooler on the intake side.
I have also heard that only the turbo models have nitrided cranks, but I can't confirm this.
Yes you can turbo a 4BD1 easily. But don't expect it to be as bullet proof as the 4BD1T.