C5R UZR

I'm contemplating a LS2 or LS3 4" stroker build. I haven't picked my heads yet, and part of the question of which heads to go with will be determined by the performance of the new FAST LSXr 102mm intake manifold for the LS3 and LS7 rectangular port heads. With that in mind, I'm pricing out the shortblock and now looking into what other parts of my build I'll have to upgrade in the process to complete the longblock.

So, I have a 1998 Vette which has the return style fuel lines that all the FI guys run quite successfully. I'd like to just keep them, but I know there are differences, though I'm not sure what (height and possibly spacing/angle) between LS1/LS6, LS2, LS3/L92, and LS7 fuel rails and injectors.

Currently I'm considering the following manifolds:
OEM LS6
OEM LS3
OEM LS7
FAST 90mm
FAST 92mm
FAST LSXr 102mm - LS3 or LS7 depending on heads

I know the LS6 manifold will work well with my rails and injectors, but if I want something better, what will be required to make the other IM's compatible?

I've seen the adapters that allow you to run LS1 style injectors in an LS2 manifold, but I can't see how that'll help.

I tried searching but couldn't find much except info on the fuel rails FAST sells, and there is not very much info on the new LSXr yet.

OutKlast

LS1 fuel rails will not work with the L92/LS3/LS7/FAST LSXr intake. I'm going through the same issue now. I have a 408ci that used to have LQ9 heads and a FAST 90mm intake, these could run the stock fuel rails. But now since I need to replace the heads I'm going with CNC ported L92 heads and an LS3 intake (until the new FAST comes out and gets some reviews). As part of that swap I need the new fuel rail as the L92/LS3 intakes are taller. I have heard of someone bending and finagling a LS1 rail to get it to work, but I would not want to go that route and risk a rupture or poor seal and have raw gas spewing all over your motor.

Now its kind of a pain finding out what parts you need to swap around. No one really has a list, from my searches you need a new fuel rail, new injector o-rings (if you're keeping your LS1 style injectors). Or you could go with a newer style injector setup in which case you need a new fuel rail, injectors, injector adapters for the different plug style.

Personally, I'm going to go with http://www.ls1tech.com/forums/lsx-pa...tock-sdpc.html + CNC L92 heads + injector adapter. And call it a day.

C5R UZR

I was reading that the LS7 LSXr is not compatible with LS7 rails, but is with LS2. What's the difference on the Gen IV stuff - between LS2, LS3 and LS7?