I had a 1979 380 SLC euro that I swapped out the 380 and installed a 450 from a 126 chassis. No problem. Someone already mentioned that you wil have to swap the exhaust "headers" (for lack of a better term). Also, the transmissions in the 126 chassis models are typically RT-722.31,2,4,5,x and those for the SL,SLC are RT-722.30x. I dont know that they are interchangable. They may bolt up to any of the appropriate engines but may be dimensionally incorrect for different chassis. This is only a cautionary note, this is seond hand info to me. Good Luck