I have been looking at a range of .61 engines (with rear needles) . I was very close to buying an Irvine .61 mk11 but it does not have a rear needle.. so the search goes on, i am now looking at a magnum .61 or a SC .61 with rear needle....
If you insist on a rear needle it is easy to convert any engine to a rear needle. Find a screw the same size as your needle valve, replace the needle with the screw (be sure it is short enough that it doesn't go into the spraybar), buy a remote needle from K&B or Fox, or where ever. Mount the needle to the backplate, firewall, or motor mount. Now you have a remote needle. Oh when you plug the spray bar, it's a good idea to use some locktite or gasket sealer to prevent fuel and air from leaking past it.