I already needed to hook up my old school front shifter since my 8 speed 105 died. I was wondering if I should just go with the rear shifter old school as well..A triathlon is not something where speedy shifting is all that important......any thoughts?

Well, having had DT shifters, I would say, WHAT ARE YOU THINKING?!?!?!?!? I would get some bar end shifters and put them on the end of your aerobars (now that you have a good excuse) or put them on the drops (assuming it is a road bike, and seeing as you have sti shifters it probably is). DT shifts are annoying, and if you have any sudden shifts, you will be all over the place. so bar ends on aerobars or drops is my recommendation. or just try to ebay some old sti shifters.

Yep, bar ends all the way. Its not about "speedy shifting". It's about staying in the aero position and being able to shift.

Something like these which are 8spd compatible

I was able to use my down tube shifters in the ends of my aero bars with some old bar-end shifter adapters. Remember, bar-end shifters are the same as down tubes with a more ergo shift lever and an adapter piece to fit in the tube.