I'd run a Performer RPM or RPM air Gap and a 4777 650 DP on that combo.

The TM5 is a very good manifold, good top end power but suffers from the smallish early 70's technology plenum for torque. If you ran a 4 speed I would probably just keep it on there...you could do a lot worse. There are better Single planes out there but on your mild combo it might not be worth the swap in terms of 'real-world' et/MPH. What hurt the Tm5 was it was not much better than the Torker and not as strong as the Victor

The RPM is just a great all around manifold for a 340 where the bottom end-through upper middle is going to propel the car mores than the top of the power curve...really your best choice, or certainly your most fool proof that it will be an improvement over what you have.