Chainsaw Repair

I tried to list the major components and really not much is used between the two models.   

6700's basically share parts with the 5500 except for the crank.  Early models had the two piece ignition.

670 to 8000 parts interchange;
handlebar - yes
handlebar support - no
clutch cover - no
recoil cover - no
top cover - no
carb - no, choke positions are different.
cylinder - no
muffler - no
intake - no
auto oiler - yes
thumb oiler - yes
on/off switch - yes
air box - no
crankcase castings - no
bearings - no
clutch - sometimes, depends on when manufactured.
crank - no
piston and cylinder - no,  6700/670 is 50 x 34mm and 8000 is 52 x 38mm.
rear handle / gas tank - no, 8000 larger.
igntion - sometimes, depends on when manufactured.
brake levers - no
brake mechanisms - some compatibility depending on when manufactured.

Hope this helps.