After market silencer for TM400

[OldTimer]

I'm sorta toying with the idea of putting an FMF Shorty silencer on my '75 TM400. It has a stock pipe and I wonder if anyone knows the dimensions of a big bore shorty or where I can reference the information?
Specifically, I'm interested in the bore sizes available. Of course the length is important as the stock pipe tapers to very near the back fender, but I think I can squeeze one in there.
Along those lines, the stock "pickle" silencer appears on e-bay from time to time, but I wonder about it's silencing ability. Also I wonder which would be better tuned for the bike. I know the stock one would enhance the value, I just wonder whether it would enhance the performance as much as a more modern aftermarket product. :think:

 

[Rotorranch]

As I recall, those things were loud! :coocoo:

I'm sure the stocker would be more valuable. But a newer style one would be quieter. You should be able to adapt a silencer to fit, but I wouldn't butcher the bike to put a newer one on it.

FMF should be able to help with dimensions.

Rotor

 

[fatboy570]

Circle F Exhaust makes a complete exhaust for the TM 400. I think they may be able to do a slip on silencer as well