suggestions for a base trike

[Sawfly]

sup, i need to know what a good base trike would be to fit a 1400cc engine in, i need something that requires minimum modification. as a last resort i need to be able to fit a 670cc engine, the 670 is currently not for civilian sales but hopefully should be by the time i get around to building this. any more assistance with specs is appreciated. this'll be my first build so whatever you got, i want. including brake suggestions, suspension ideas, and anything else i'll need to know.

l8r

[Mosh]

Welcome to the site, and I hope all is well with you being over the seas defending or Country.
Thank you for your service.

I personally have no experience with cramming bigger engines in trikes like you want to, but some people here have put some CB 750 engines in some Bigger sport trikes like Tecates and 250R's and the like.
Most of the guys doing what you want, used the street bike frame for the engine and found a way to adapt a live axle swingarm on the street bike chassis.But some have cut the engine cradles in the frame and added some tubing to make the chassis fit the larger engine and re worked the engine mounts.

Any "Production Trike" frame you use will have to be heavily cut, re-shaped and welded and modified to install a engine of that size.
The biggest Sport frames available is the Tri-Z and Honda 250R and Tecate 3.
Either way, there will be a fair amount of work and a handy welder to do what you need done.