Too old you crack me up
Seriously though lilyput welcome to the forum
Don't even start to worry about your age I was 47 and 120kg when I started bocking and I'm still 6ft 4"
so you should be young enough
With the current series of bocks I would recommend getting your exact weight so you should be looking for the 90kgs but ask if they can find them in the mid range as the 90's go from 90 to 99 kg (all stilts are marked on the bottom)
The trouble with asking for an exact weight is that they have to open a lot of boxes to find the right ones (boxes are only marked in 10kg jumps) so they charge a small summ to do it (understandable as time is money nowdays)
Having said that if you get 90's they will be easier to learn on and if you get 99's they will take longer to learn on but you won't need to change the springs as soon (most people go up in weight a bit when they get a good technique)
Most important bit is get wristguards and elbow and knee pads (I would also suggest a cheap skate helmet for the first few weeks as you could be in the minority that fall on their head
)
Also get along to meets as soon as you can even if you can't walk you will learn so much quicker amoungst other bockers
Jason