The dynamite kit is not made anymore. 10 years ago, even after they were discontinued you could occasionally find new in box Dynamite kits on eBay but not anymore. Btw they're the most expensive but also the most comprehensive big block kits as they also included an engine, exhaust and a complete (6) cvd kit. As as far as I know RD Logics and AcncM were the last ones to make a big block kit but they also stopped years ago. Nobody makes a TMaxx big block kit anymore.

The used market and making your own are really your only options. Making your own would require making a new, longer chassis plate that's extended in the rear to make room for the longer big block. If you can do that the rest is easy. You can go the cheap route and make a new extended rear skid plate or do some cutting on some chassis braces. Personally I'd cut a set of chassis braces just behind the trans mount, then cut another set just in front of the trans mount. Make a custom center skid to tie the braces together using the skid plate holes already in the chassis braces and that part is done. Get some of the big plastic sliders used for going to the wheels, cut it down for use in the rear and your done.

Or you could do what most have been doing, just get one of the bigger engines that bolt right in place of the stock engine. Unfortunately the Picco and RB are no longer but there's still OS and Novarossi. If you want your TMaxx to be big block length get the newer 3.3 extended chassis to go along with it, it's the same wheelbase as a big block. Well except for the Dynamite kit, that's 1/4 inch longer than all the others.