"The best warranty is the one you never need to use.....SWAMP"
You cannot forget MAS either when talking car motor builders.
GTO has been aligned with MAS for years.
WaterThunder, Branch and MAS have been in the game a long time and have proven reputations for engines that stay together and make good power on airboats.
I met a guy 4-5 years ago up in a little spot around Levy County. He had a WaterThunder engine that was beyond bad ass. Talked with him a bit and learned he was affiliated with a NASCAR Cup Team. That should tell you something right their. I got with Dave and he verified it and if I recall the conversation there was some very special head work that was done to that engine.
Wish you the best in your search for a quality build, may you get years of trouble free rides!