well I just finished up my swap. had a rusted out 87 300sdl with 160k on it that drove great. picked up a mint 350 with a questionable engine, swapped them out and I am a happy camper! I searched briefly but couldn't come across anyone that had done this swap, but I'm sure there's gotta be a bunch. Anyways, the list of things I had to swap from the donor car are as follows:
accelerator pivot arm reciever that bolts to the firewall (350s use a slightly different system)
glow plug relay + harness connector (eliminate fifth white wire. other 1-pin 300sdl connector still snaps into 2 pin 350sdl connector on the green wire)
big A/C hose (350s hose will not bolt to 300s compressor)

things to KEEP on the 350:
power steering tandem pump for ASD
dual radiator fans


aaand that's about all I can think of right now. everything else bolted up without a hitch save for some minor vaccum line eliminations. new car drives great and I'll post pics once I'm done with the rubbing compound/wax!

__________________
1993 2.6 (040) SportLinE 5-speed - Armed to the teeth w. roof rack/2x bike carriers/8x ski carriers/MB towing bumper
1993 2.6 (040) - deceased/reincarnated as a trailer.
1987 16v (702) - Now parting out(9/22/10)!!! - Email me your requests for 16v parts- Engine and full body kit avail!!
1987 300SDL (122)- For sale!

I'm interested in the old glow-plug relay from the 350SDL if it works.

__________________

Gone to the dark side

- Jeff

sure, 60 shipped

__________________
1993 2.6 (040) SportLinE 5-speed - Armed to the teeth w. roof rack/2x bike carriers/8x ski carriers/MB towing bumper
1993 2.6 (040) - deceased/reincarnated as a trailer.
1987 16v (702) - Now parting out(9/22/10)!!! - Email me your requests for 16v parts- Engine and full body kit avail!!
1987 300SDL (122)- For sale!