I did my FAA ME CPL and IR with Riverside a couple of months ago.
Can't recommend them enough: very friendly, top quality instruction and Tulsa's a damn good place to spend a month or so in (actually, too good
). Yuri, the CFI there (Tony Cornish's son), runs a tight ship and will certainly not rip you off (I have three anecdotes to support this if you care to PM me).
As for subsequently converting, I found that after 16h of IR training I felt prepared to take the test, although I ended up doing 20h.
I converted with BCFT, and found them to be very good as well. An advantage of converting with Airways (Exeter) is that Riverside and Airways use the same checklists for the BE76.
I've posted before concerning Riverside- just do a search 'all posts by WX Man' and you'll bring a few things up.
Any other info you want, please feel free to PM me.