Toyota "B" series diesel engines ???

[FSJer]

I have a 89' toyota landcruiser 4x4 that currently has a 2LT , but am building a 13BT soon . I am seeking inforoamtion as to whether i cab drop a crank from the larger 14-15B into my 13BT . the larger models have a longer stroke , but not sure if its a direct fit ? also wondering if you can put a 15B - 16 valve head onto my block ( 13Bt is a 8V head ) ???????????