If you're not making it removable, there's really no need to use an IGT frame then as the basis.. Just some aluminum angle iron spaced the appropriate distance will allow you to capitalize on the modularity of the IGT components, and be a heck of a lot slimmer in the process...
For slides, start here:
https://www.accuride.com/en-us/product-catalog
For slides, start here:
https://www.accuride.com/en-us/product-catalog