EzGo TXT engine locked up looking for options/opinions

[borkap]

I was on my home from dinner and my 1996 + (not sure of the exact year) TXT locked up. starter was turning and motor wasn't. I grabbed the primary and tried to turn it by hand and it was in fact not going anywhere.

History:
I bought this cart in bad shape and rebuilt the top end and head, reason i did that was an exhaust leak due to a broken bolt in the head. I fixed all that new gaskets, rings and cleaned up the valves etc etc. Cart ran like a champ after that.
I changed out the lift and tires and some other stuff. (not really relevant)

That cart ran fine on our way to get dinner then on the way back I heard a chirping and the lost power. I pretty much alreay knew it was locked up then.

All this to say I need a motor or to rebuild it. To that end I am seeking guidance on what to do.

I am handy and can rebuild motors etc.
I'd like to keep it as inexpensive as possible.
I love the idea of the v-twin but they all seem so loud and they are expensive
I am leaning toward a 350 but not sure of cost or gotchas
I will probably change the clutches as well to get more bottom end.
I'd like to be able to maintain at least a 19 MPH top end with improved bottom end.

If you were in my shoes what would you do?