The questions that come to my mind are:
- Are you willing to chase down port tubes and mounting hardware that fit the existing holes in the baffle, and then install them properly?
- Are you willing to buy and install damping material inside the cab?
- What is the maximum amount you're willing to spend for a pair of drivers?
- Do you want to save a few pounds and go with neo magnets, or are ceramics acceptable?
- Will you add a high pass filter (additional cost) somewhere in the signal chain to protect the new drivers from overexcursion, and leave it set at the frequency recommended by whoever does the modeling no matter what?
- Will the cab be under your supervision 100% of the time so that it doesn't get blown up the same way as it is now by people who are ignorant of these matters or just don't care?
And one comment, which others have said and I will repeat: In my opinion the resale value of such a cab, once finished, will be nowhere near what you spend to do the job properly. In short, don't fall victim to the "sunk cost fallacy".