6.4 hemi

Personally, I think a set of swap mounts and a stock k-frame are the most cost effective method to swap a G3. It's pretty scienced out now. Heck, Holley even has their swap headers back in stock.

Certainly some of it is dependent on end goals. A max HP build might want a COC like the HDK so they can run big long tube headers. Another option with a COC is the use of the OEM 6.4 exhaust manifolds, can't do that with a stock K-frame. Or if you want PS but don't want a Borgeson box, then (I think) a COC is the only path. And Denny has worked hard on engine placement and might be able to save some cutting on the floor if an 8HP were used. Plus the lack of TB and clear space is huge. So there are advantages. And I would add that if I was looking at COC kits, an HDK would be the winner in my mind. Just keep in mind that there are disadvantages too, and in this context cost is the number one.

For me, the Holley swap parts are the bomb. Gives clearance for the SRV module so I don't have to cut my firewall or lose the SRV option, I can run the stock car FEAD including the low mount AC compressor (VVT motors only) and there is an oil filter adapter that works so I don't have to run a remote filter. A COC doesn't need one either but the Schumacher/TTI kits requires work to avoid them. And the Holley swap headers are stainless and like $300 less than the polished TTI's. The disadvantage is the Holley mounts are for '73+ V8 k-frames only and they move the motor forward 1.75" and forces transmission mount and linkage work. So they are kind of a downer if someone wants to run their stock auto or 4 speed, but that doesn't matter if a 6M/8A is being used. It's not free for sure, I am $1500 into the parts to bolt a G3 into my car and I already had a k-frame. Current costs are certain to be higher but pretty sure it kills the cost for a COC if that is the only reason

Be aware that using a TR6060 from a Challenger with a stock k-frame is difficult. The idler hits the starter and requires an aftermarket starter and a custom starter mount. Add that an aftermarket shifter will be required (stock is divorced), an adapter to make the driveshaft work is required and there are no outputs for speed. Plus I have seen several stories of people buying used TR6060's and having problems with them, so I dropped the idea and bought a T56 Magnum kit and got a brand new trans and dodged those issues.

Here's another example of a 6.4 swap but using the stock k-frame and shifting the motor forward just 1/2"-5/8".

https://www.forabodiesonly.com/mopar/threads/things-change-butters-is-now-getting-a-392.552780/