Which SB?

So the 67 cuda I scored came with a 2brl 273, complete. Popped the valve covers yesterday and found an adjustable valve train and I'm betting there's a forged crank in the bottom too. Here's the query. Do I rebuild the 273 up right or do I do the 69 318 in the garage?

If I go 'teen: Can I use the forged crank from the 273? Heard different things regarding this (Allpar) and need a sure answer.

The heads from the 273 are the small chamber (57cc) casting. Make a good swap on the 'teen to help bump compression?

Lastly, to go with the adjustable valvetrain or is this something you always have to F with? Is the benefit of it that great over the stock type shaft rockers or is it just more headache?

Many thanks in advance :)