383 power upgrade help

Okay I think I’ll just get that kit then and does anyone know any good rocker arm shaft and assembly I should replace the old one with I just want to be safe since it wasn’t tightened down it might be bent
Take everything off the rocker arm shaft clean it up, and then roll it across the table top and see if it's bent.

I would not just go throwing money at parts. I would make a list of what I think I need or do need and study the list before I go buying anything.
Starting your list should be a new oil pump, a timing chain and gear set, and a gasket set.

If you spray some Degreaser or something on the top of those pistons and wipe them off you may find the part number and the oversized stamp on them. The part number may be on the bottom of the piston also.
Then we can look up the part number and tell you pretty much what compression ratio you have using those close chamber heads.
If you want to check for the top dead center measurement put the harmonic balancer bolt back in the crankshaft and take a socket and breaker bar and crank the motor over to where a Piston is at the top of the cylinder. It doesn't matter which cylinder just any cylinder.