Komdotkom

It basically boils down to put the longest rod into the engine that you can afford after you have chosen your engine. If you have an L28, then depending on your budget, put the longest rod you can afford into that. If you were really keen you could use FJ20 rods and custom slugs, but that's going to be a $3k exercise. If you aren't racing then just run L24 rods in an L28, bore it as big as you dare. Cheap and easy.

Just to clear things up a little, your static compression ratio really doesn't dictate if your engine is going to have detonation issues. I run 12.4:1 on 98 RON, it's fine. What creates detonation is cylender pressure, this is influenced by a number of things. So you could be running 12:1 but only have 180psi in the pot, so it will never ping, provided you can tunel. So static C/R is a nice number to play with, but your cam profile and timing will have a huge effect on your cylender pressure. In my experience, good L race engines run over 225 psi in each pot to make decent power. The longer rod isn't really much good for decreasing you chances of detonation, well not the small changes that we are talking about. I run longer than stock rods to reduce the rod angles and friction on the bore. Getting back on topic, a 3.1 with a fairly poor rod ratio of 1.6 and low comp will eat a highly strung l20a with a long rod ratio, unless you plan to spend 10k on a gearbox.

Nascar have been running Honda big end rods for years now. The big advantage of this is that Honda supply bearings in minute increments which allows you to get things just right. Grinding the big ends down gives you a number of advantages, you can increase the stroke without welding, but it also allows you to put a much nicer radius on the crank than standard. This needs to be done by a quality operator though, as too much radius can cause the rod bearing to pick up in the radius. I always have my cranks nitrided and then ground, after the grinding it's off for cryo treatment. I consistantly spin my v07 crank to 8200rpm with 48mm big ends, it's never broken. If you are going to do it, do it once the right way.

Grind you crank to match the toyota rod, centre the rod on the crank during this process. This will not weaken the crank, anyone who tells you this is not talking from experience. You will then need to mill the pin end of the rod 2mm each side to fit the piston. Simple process, any competant machine shop should be able to do this. The pin diameter is 22mm for Z31 and 3sgte

They are from a VG30E Z31. depending on your head / cam selection you may need to cut valve reliefs in them. Should be ok with P90 and 91 RON fuel.

Just going back to possible combo's you could run 88mm vg30 pistons with toyota 3sgte 138mm rods to give you a nice rod ratio and flat top piston without breaking the bank. These engines work really well, but require the cam timing to be spot on to achieve best results.