Common man newb observation. This may sound flippant and sh$tty. I assure you it's not meant to be.
If your (responsible) tac is not 'rip down the road in 3rd' with the goal of 'a little extra boost when you need it' dynoing a JB4 seems excessive, both in terms of your driving goals and cost. They're great cars as they sit. I have read thousands upon thousands of posts on here...never seen a dyno for a jb4...along with your tuner won't touch it. That's a clue, i think.
Unless you are expert in tuning, you're missing the key benefit of a $250-350 dyno session...it's not safety. It's having a pro tuner, in a controlled environment, watch and adjust the car/tune between each hit. That's invaluable and immediate
The more reasonable (common) approach would be pedal commander, followed by JB4 maybe, if the PC isnt enough, in terms of feel for you, behind the wheel. You're at around $800 bucks on this (w/o dyno...add dyno you've reached a grand....but the above still applies.)
Other option, is an off the shelf, canned EcuTek tune...no dyno required. Those are strongish, not crazy, safe tunes on a healthy motor. Plug it in GTG off the shelf. Should you decide to bolt and 'turn it up' that option is there. Same money...$1000 give or take.
So cancel out all my observations...take the car and Jb4 to dyno make your passes. Without tuner help, you leave, study, get help from here and then need another dyno session to confirm positive changes and motor safety. Again....JB4 and two dynos...you're at a grand.
Plus, the generally preferred method, an ETek tune is much, much more than a boost controller, in terms of items that can be adjusted....way more bang for the buck than other options.
So I'm assuming, on the parts, you have $800-1000 to spend. Maybe consider different, 'stronger' options for your goal.
Of course the most cost effective option to meet your goal quickly and easily is research your area for a flat vacant road, install JB4 with fuel wires and start doing 3rd gear pulls and posting data here. If your willing to buy a used unit - always available here - you can pull your cost down to a few hundred bucks and be GTG in a couple of days.
Food for thought.