I have an old bike with centre pull caliper brake and I am thinking of converting it to a V-brake. Do you think this is possible?

Edit: I misread the OP and thought they were talking about switching from "cantilevers", not "calipers". V-brakes require the studs that cantilever brakes use.

Yes, it's possible. V-brakes usually require a longer cable pull, in which case you'd need long pull brake levers. But short arm v-brakes use cable pull similar to cantis. The length of a v-brake arm is in its specs. Here are some:

https://www.gravelbike.com/v-brake-arm-lengths/

I think for 85-90mm or longer arms you'd want a long pull lever (just guesstimating - research this a bit). You can get long pull levers for drop bars or flat bars, but I don't think there are long pull brifters, so if you want brifters you'd need a short arm v-brake.

Center pull, other than cantilever brakes ,
bolt onto the fork crown/rear stay bridge..
V brakes need 2 posts on the frame.. as do cantilever type..

But a workaround ,, from BMX, was a bolt on arched plate ,
with the V brake posts on the plate..





..

Oh yeah, you're right. I misread "calipers" as "cantilevers". I edited my post above.

If you don't have studs for v-brakes, another option might be modern dual-pivot side pulls. If you keep an eye on the online retailers and Amazon, decent pairs of Tektro brakes show up once in a while. You have to observe the dimensions and mounting styles to match your frame. I've done this on two bikes, and those brakes are just superb. They also seem to require less fussing than v-brakes to keep them centered and adjusted.

Dual pivots rock. They stop as good as anything else in my book.