I'm assuming that, for whatever reason (maybe there is more room in the 70 series between the bellhousing and the steering gear) the 70-series starter is longer than what would be in a 40 series. You need a starter that will spin the 3B, but also be compact enough to fit the engine compartment of the -40.
At TOYODIY.com there are four starters listed for the B/3B series motors just for my 03/81 BJ40 (let's assume that the 1986 3B is generally the same as the 81 B for purposes of the starter.
28100-56080 (12V with EDIC),
---56090 (12V w/out EDIC)
---56070 (24V with EDIC)
---56100 (14V w/out EDIC).
You can always search for a later BJ40 if you're concerned about the year difference, but I wouldn't sweat a few years; if it's a B/3B series engine, going in a 40-series chassis, you should be OK with the above. Once you have the right part number for your 12/24V, with or without EDIC engine, you can just google it (followed by the word "toyota" so that google doesn't treat it as a subtraction problem!) and you'll find vendors for a starter that will fit.
HTH,
Travis.-