There is not such a dumb question, only the question that never gets asked is dumb. lol
The big question is: Are you gonna be racing this kart at a national level? Club level, or just the weekend warrior and an occasional small club race?
Most guys used to convert their shifter karts from 125cc to 125cc TAG karts, by removing front brakes, spindles, brake bias, shifter levers, etc. Yes it is doable, as the chassis were built stiffer to endure the max torques and bangs from the 125cc’s
But once again, the big question is: What are you planning to do with the kart?
Another thought would be if you don’t have a complete engine package, it could get pretty pricey by the time you’re done piecing it together, rather than just buying a complete TAG package for a decent price?