Do any other frames interchange with this bike?

[chewy4x4]

I was wondering if slash 5  frames were interchangeable with that of the 1978-1984 R65?

[Rob Valdez 79 R65]

Only if you want to build a /5 with a R65 engine in it.  

They both use the same steering head bearings, and possibly the same swingarm bearings.

All manner of brackets & tabs will be different.  The /5 had all of it's electrics inside the headlight shell.  

And the /5 frame was lacking in certain frame stiffeners that came about when the R90S was introduced.

Foot peg mounts will be different - you may not be able to use your kinematic shift linkage, which would be two big steps backward, IMO.

No doubt I have missed a few things.

[chewy4x4]

I was wondering mainly for seat inter changeability but I figured that would be the case.

[Rob Valdez 79 R65]

Are you saying you want to put a /5 seat on a R65?
In that case, you might be able to put a /5 subframe on a R65 frame, as long as it doesn't mess up your shock geometry (probably wouldn't?).

And the R65 tank is longer than the /5 tank, so there would be variables to work out, there, as well.

Please state exactly what & why, and it might be easier to come up with answers.

[chewy4x4]

I want a cafe style "sport seat" I believe that S. Meyer has one for the R65 but its not listed on there site. Also as it has been said before the Corbin seat for the /5 is quite nice. I hadn't thought of the sub frame swap.

[Rob Valdez 79 R65]

If you don't care about the seat hinging, you might want to consider something from these people:
http://caferacingparts.com/  
If I ever get around to building my CB200 cafe bike, I am going to use their DUCBTA (it has a tail light).

Where did you hear about the S. Meyer seat, if it's not on their website?  I know they sell on eBay from time to time.

[nothing]

My "R65" has a frame from a /6. The quotation marks are present because the frame means it's legally not an R65 at all - it's titled and registered as a 1974 R90/6, since that's what the VIN says it is.

More interchangeable than most seem to realize.

[chewy4x4]

Nothing again it seems your bike is probably a r90 with a r65 engine. I was asking because I wanted to know if the seats of any of the old bikes were interchangeable. Oh and rob it was from an S.Meyer eBay action that I asked specifically about the seat. They say its not listed but it exists. I wonder do they make there products? if so maybe they make the adjustment for the R65.

[Rob Valdez 79 R65]

S. Meyer is happy to correspond via email.  I recommend contacting them that way!

[Rob Valdez 79 R65]

Nothing again it seems your bike is probably a r90 with a r65 engine. I was asking because I wanted to know if the seats of any of the old bikes were interchangeable. Oh and rob it was from an S.Meyer eBay action that I asked specifically about the seat. They say its not listed but it exists. I wonder do they make there products? if so maybe they make the adjustment for the R65.

Well, I found the solo seat for our standard R45/65's!  It is for their police bikes.
http://www.realoem.com/bmw/showparts.do?model=0364&mospid=51897&btnr=52_0987&hg=52&fg=05