I've read for two days, lot of great info on here. I've came to the decision from all the post I've read and research I've done that Backwater has probably the best LT Mud Motors and kits on the market. I however cannot afford/justify $1-2k for a frame kit. I'm not a machinist but I can cut and weld steel. As you already know some parts can be purchased from Backwater to start your own build. The drive shaft listed is 3/4 diameter. Will this be sufficient for 22hp?
Now I have also read some comments in other post "Thai kits are not good for stump areas, get a Backwater kit"! How would the backwater differ other than better quality from a Thai kit relating to stumps. Areas I hunt and fish contain it all, marsh, pads, mud, downed logs and brush and cypress knees and stumps. Is it the design of prop installation or material of prop? A lot of you have have already been through all of this, all the parts I would need from backwater, bearings,u-joint, and 3/4 drive shaft are less than $600, is it worth the trouble and time.

Wondering the same

After more research and reading on here I think I'm going to build my own. I found one on here I liked, if I win the lottery I would probably order me one from BW. It may not look as good, I know it will be as durable and I am totally satisfied it will be better than the Thai kits.

If some day I'll decide to built a custom long tail, the first thing I will change will be the diameter of the shaft. Just by go up to 7/8" will give you less trouble and also will change the prop thread for a different system, because it is the weakest link.
P.B.

Here is an idea I have been thinking about... Contact Beavertail and see if they will sell the hard to fabricate parts for a surface drive and build one of those. They have a parts manual on their web page which show parts for all the components to their SDs. I have built two LT and they worked just fine but I'm thinking SDs are much better. Like you, if I had a pile of money I didn't know what to do with I would buy a new one.. Just giving you something else to think about.