First welcome to the forum.
I will take the opposite side of dave.
If the frame is name brand try to find a slide of the same brand. 175.00 should do it for most.
You have one problem in my opinion. the 45 ramp is cut deeper and further forward than a 38 super If you go with a ramp barrel you will cut MOST of it out, a non ramped barrel (on a ramp barrel the ramp is part of the barrel and you cut the one out of the frame) you may very well have problems with feeding.
you did not mention if you will reload or shoot factory. with more std loads you will not need a ramp barrel for support.
Factory Colt or springfield 38 barrel should set you back 75.00
extractor ejector firing pin stop firing pin (needs to fit well, espically with springfield) and sights you might as well buy new. It is a project, and you may need professional help to get it 100% at the end.
(take that one either way
)
hope this helps
geo ><>