(Newbe) 273 to a 340 and tremec 5speed swap.

Young blood, make a plan and stick to it. It`s the only way things get done.
Good luck.
I also have a 67 notch. It was born a 273 2bbl, 904, 7.25 rear. It had a 318 when I got it.
I wanted more and sourced a 69 340 with it`s #`s 4 speed and an 8.75sg rear.
That configuration is a blast, plenty of power. If you experienced a 340 notch, you`d probably fall in love and may never want to get rid of it. I did and am still enjoying it after 27 years.
We`re die hard Mopar fans here and most of us probably don't like to hear the word flip.
You should of kept that to yourself.