those couplings bolt right to your flywheel/crank flange
as far as the spline - you need to measure it and determine what spline and go see your Cat dealer's Marine/Industrial engine TC (technical communicator) or service manager and try to see if any of those Cat couplings will work
If the trans you have is not a match, then you'll have to pick the closest and enlist the services of a machine shop experienced in that sort of fabricating.
As far as engine mounting to the trans - I dunno what you're dealing with - dry housing/wet housing....if this trans is not similar to what Cat couples the 3056 to, maybe you have a dream...
but generally, you just hang the engine on the crane next to the trans and start measuring/drawing/welding/spending/fabricating
It's called "fitting"... it's the sort of work millwrights and mechanical fitters do. There's no plug and play adapters for two incompatible units. It's all custom work. Alignment is critical.