Well for one you don't need the S15 core support unless you absolutely need to replace your stock core support. All you have to do is cut holes behind the headlights in the stock S13 core support and trim the support wings that run outsite the innerfender apron. They are there for the sake of stock S13 fenders mating to the stock core support. you cannot put your fenders on with the headlights unless you trim them off. Yoshi did a whole write up about this.
If thats your S13.5 in the pic its nice. I have been planning on doing this conversion for a long time and have collected my parts as well. I will be running a factory front bumper with the gracer lip ( thanks woodchuck)
. I do like the spec R bumper in your pic though. Is that car using widebody fenders or stock style? Plus I am probably going to deal steel fenders as well.