At this time I would recommend getting the Taylor K-2006 and extra reagent for the CYA test and since you're dealing with a plaster pool and are probably going to do a lot of calcium hardness testing, get extra reagent too. The kits are usually available at pool stores but a good online source I've used is
http://www.spspools-spas.com/
and their bulk reagents are well priced too.

Al