Stall, for a given flap/slat setting combination (just flaps on a cub) will always be at the same AoA.
AoA is also a much better indication of loading and proximity to the stall than airspeed or a g-meter. But, unless somebody's done some considerable work to produce operating data based upon AoA, calibrated the instrument, etc. it's not a great deal of use. On an aircraft like the Jaguar, Tornado or Concorde, it's essential. I'd venture that on an aircraft like a super-cub, it's usefulness when you have adequate stall warning from things like lack of wind noise, back-stick and buffet, is at best marginal.
If you simply want to fit it, as something to look, then it's probably a minor mod. If it's on a permit, the PFA'll do it for free, if it's on a CofA it'll cost you £62 through your CAA regional office. They'll probably insist on a suitable placard being fitted saying that it's not a primary flight instrument.
If you want to make proper use of it, that requires calibration, flight testing, preparation of a POH supplement and CAA major mod approval. If you want that, the CAA minimum fee is £309 and you'll need the services of an E3 company, or design and flight-test signatory acceptable to the CAA. Offhand, if you were to ask me to do the job, I'd probably charge you around £2-3k. Trick is to find a design signatory who fancies free use of a super cub for a while in payment, that might be me as well, but even at my eminently reasonable consultancy rates, that's a lot of flying!
G