G1355 and the 585 engine are not as bad as you might think. There's a couple upgrades and maintenance tips and they will run FOREVER. Also, I've learned you don't look for 585 parts in normal MM collector circles or you will pay too much! If you'd like a pretty good authority on these beasts, email me. I can put you in touch with him.
Otherwise M670 and G1000 are plentiful and have many parts in common. The cheapest fun would be an M5 if you'd like a wide front diesel.