Your Transmission is a Baker Hill 5000. It could be swapped with a Baker Hill 7000 if you want to keep your reverse and upgrade your machine a little bit. You could also throw in a Baker Hill 6000, but you lose your reverse with that. As for the engines, Vanguards can be had relatively cheap if you keep an eye on craigslist and ebay. If you just want something new to through in there and will get the job done, harbor freight sells a 16hp honda clone that many members have had good luck with.
l like to buy stuff and no I don't do payments!