I suppose it migh make a difference what sort of 1911 you want to build,but I believe Caspian is an excellent product,and the frames start at under $200 retail.
You might look at the Fusion Firearms site at a kit,but,I have zero experience with them.
I have come to learn that ramps,while advantagious on smaller calibers such as 38 super and maybe 10 mm/40,may have a problem with 45's.
Reason,given the top of the magazine is in the same location for all of them,the center axis of the feeding 45 round is lower.
Depending on bullet profile,a 45 is more likely to collide with the ramp and stop.