... I've seen the 'toaster pickups' on all the t-40's i've seen, what do the other ones that I should avoid look like?
The "toasters" are the originals. The later "blades" look just the same, except for a strip of metal across each of the black inserts. Internally they are different, as "blades" use only one magnet. They're reported to have a slightly hotter output, but less "warmth", however that may translate. I personally don't feel there's any reason to avoid them. It's more of a snobby thing.
Also, are there particular years of production that are better/worse?
Not really. Hartley Peavey was the first to implement CNC-aided production, and T-40s are very consistent structurally. Those from the 1980s have a bit more contouring, and some of the painted ones from that era may have lighter alder bodies instead of ash.
EDIT: TBer Eilif is our inofficial curator of all things T-40, and you can read his fact sheet here:
http://www.talkbass.com/forum/showthread.php?p=5608727#post5608727