I agree with Bubba22349 in that it would depend on your goals for the car. if your goal is to sell the car at auction, then its not a missed opportunity, its just getting it back to its highest value for collectors. or if you like the idea of keeping it as factory original as possible, then go that route; if you just want to drive it everyday and want to increase its road reliability, then a mild-cam, tighter valve springs, double roller timing chain, roller tipped rockers (not double roller rockers), would definitely be on the wish list for the rebuild.
bottom end doesn't NEED a lot of work, but I would personally look into the Toyota 1JZ-GTE H-Beam con-rods, and if they are ideal for what you are wanting, as they would need to be shaved to fit in a SB6, and the crank journals would need to be turned down to fit the 1jz crank bearings.
I also agree with bmbm40 in that a completely factory rebuild is a wasted opportunity, even on a 170. there are so many things that can be done to the inside of the engine, without changing its sound, but increase reliability, and usable power-band that it really is a missed opportunity to rebuild either engine back to stock, but that is taking into account the goals I personally have. it may not be what you want at all.