Any recommendations for building a '73 340?

2-3 K budget.
You just ate 1/3 of that up with good headers and intake if you buy new.
I would put some Keith Black 243 pistons in it. Balance the stock bottom end.
Re-do the heads you have, and buy a McLeod flywheel that takes the bolt on weight.
Match it up with a cam and valve springs of your choice and you will have a nice strong street friendly pump gas motor.
You should end up around 3K with careful shopping.

The KB 243's with stock x-heads put me right at 9.1 compression in a 72 340.