I just found this topic. I am the owner of the company who was planning the O scale Budd Silverliner MU car kit in conjunction with the Cherry Valley club a couple of years ago. Unfortunately, that project was dropped because of a lack of interest and the fact that the CAd company that did the work for us on the body lost the CAD file. Since we are now doing our own CAD, it's now a future project to do it over again.
A couple of things:
I myself have been interested in the Metroliner MUs since I was a kid, and have plenty of documentation on the cars, including paint chips from the Capital-liner scheme of the 1980s on the rebuilt cars, Amtrak maintenance guides, operator's manuals, and notes I made myself. I was fortunate to ride them in their last self-powered days in 1987.
I just today got ahold of three of the old Clark Benson O scale extruded aluminim Amfleet car kits. I was looking at them and thought immediately about converting one into a Metroliner MU. (Clark Benson did make Metroliner MU kits, but try to find one!) The CB kits were made using Williams Amfleet extrusions cut to full length and injected plastic ends, and he made his own hardwood floors and cast-metal Pioneer III trucks and underbody. The kits look decent when built from the photos I have seen of them, but I can see making all-new tooling for trucks (power and dummy) and underbody to match the Metroliners as built. I figured the Williams ends and pantograph would work, with a little re-milling of the CB body shell at the cab end to accomodate the cab piece and allow for its length. I am looking at doing cars for 2-rail operation. If it works, and if I actually find the time for this project, I will try to keep everyone posted.
Also, if there is any interest at all in a resin body kit for the (Budd) Silverliner in O scale, please let me know.