Don't forget timing chain guides while you're at it.
Look in the parts forum. There's a C36 engine for sale. A long time member installed such an engine in his 300TE with great results. I'm sure he'll be willing to pass on his experience.
At the very least compare the cost of hopping up an M103 with swapping in an M104. I think it'll cost less in parts, labor and analgesic to go with the M104.