I was thinking about updating my board but I guess I should find the volume of my existing one first (wouldn't be too happy buying the same volume again )

Any suggestions as to the best way to guesstimate it?

I just started using my short board again (when I first purchased it there were only 'floaters' & 'sinkers'?) and I want to upgrade my rig. Currently it is a tie-on-boom, one piece mast and Tyronsea base. I guess the base is going to be the major hurdle because of the fiberglass board's age (mid 80s). Pics of what I got:







First question is would the newer rigs fit on my existing mast base? Guess the gear I'm looking for would be
- two piece mast
- clamp on/adjustable boom
- 2 sails? (I have a 5.9 North Sail and am 75kgs)

I just do flat water at the present but may venture outside again. Only took to the surf once way back then but my water starts wernt that good, so lost my confidence .

Cheers