What's my 71 340 Demon Worth?

Yes, you can get the shift knobs in reproduction.
Brewer's Performance - Mopar A833 4-Speed Transmission and Component Specialists

As for the tips, i could very well be wrong, it looked like to me in the pictures that the round tail pipes exited straight out from under the rear bumper.
My mistake!
Tom.
No worries Tom, good on ya mate.
Cheers
Glenn.