Hi,
In terms of what you can and cannot use at the club, there aren't any restrictions.
You could also still be competetive with brushed equipment, its just harder work to maintain than the new brushless gear.
For a B4.1 I would reccomend an 8.5 motor, although if your a bit "rusty" you may wish to start off with something a little slower. I would suggest you choose from one of the more established reputable manufacturers eg: LRP, Novak, Nosram, Orion, Trinity, Speed Passion, to name a few (sorry if I missed some others).
Speed controller wise, its down to budget and what your happy to spend. Maybe read some posts in the electrics section of oOple to get some ideas?
Hope to see you at the club soon
ps: There are quite a few of us who used to race at the club 20 years ago too !!