the d17 would have more trq then the d15... if you got the time and the money id do the d17 stroker idea. thats what i plan to do too. also you could get a set of pistons that maybe bump the CR to around 10.5:1 or 11:1 which will run on 93 octane tuned no prob. to even help with the trq you could get a mild cam.
you know if you do the D17 idea you will need the crank/rods/oil pump/pistons from a D17 or similar like after market. if you get aftermarket pistons, this is a plus because they could be forged and are usually lighter then a stock piston, so right there it frees up some energy.
though i do have a question though. since the crank side of the rod is the same size as the D16 and the B18B(LS rods) couldnt the LS rods be used because it has the same wrist pin size of 21mm i think? Block notching will have to be done anyway if using the D17 rods so why not upgrade lol. though on the B18 rods they are bigger on the crank side than the d16 rod or d17, so .022 has to be removed from each side to fit the crank.
for the head, if your OBD1 keep the Z6 head too then. of course a Y8 head could be used and will bump up the CR a little more, but its what evers easier for you.
btw where can you get a d17 crank and stuff? i searched on ebay, and local yards via the web on
www.car-part.com and i couldnt find anything