I've heard of people using the twin T25 set up for the 300zx off an S13 sr20, i'd say go that route since you can purchase a used T25 for $120-$150 and buy a rebuild kit for like $90 is necessary. Also i feel like if you used the T28 you'd have to use black magic to squeeze them in so that they're not awkwardly angled or smashed against something, but thats just a guess since im not that familiar with the 300zx powerplant.