I think I'm sort of figuring this issue out - or at least getting more information on it. Several other people have written about similar issues with their 4l60e swap on other forums. Looks like it could be a TPS issue, possible the MAF sensor (but probably not), or the VSS not functioning properly. The sensor came with the transfercase adapter that Advanced makes for the 208. Could be a POS for all I know. I don't have a tuner or the money to buy one at the moment, so I'm probably going to start with a mechanic who is comfortable working with a Frankenstein to determine what is shifting ad what RPM. Hopefully from there, I can start troubleshooting.

Don't mean to bother people with my questions as a result of me not doing enough of my own homework - there really is a lot of information that is free and accessible on the web.