hey mate
the eccs redtop is the better of the lot (NICS, silvertop) that is if u change the ecu aftermarket or remap, port the head and match the manifold, get rid of the butterflies, u can port these heads/manifolds more than the silvertops, the cams are more aggressive, and the bottom end is roughly the same although it is fairly strong and can take a beating
silvertop 6 port manifold can not go on to redtop 12 port (ECCS or NICS) as the ports dont match and coolant gallery closest to the radiator doesnt line up right
head and bottom ends arent interchangeable different bolt patterns between the silvertop and redtops
loom will connect in some spots, u can run the ignitor and coil packs, CAS is different and there are 3 different redtop ones, but u can use a silvertop CAS as it bolts up, injectors are smaller on the redtops
anyway that is all i can think of, the many let downs on the redtops were the ecu, port design, inlet manifold. but if u modify them then they go fairly well, but it is hard to get gaskets now!
i preferred my redtop over the 20/30det and the 25/30det, yea the 20/30det and 25/30det had the power and torque but they didnt have the reliablity and the ability to be thrashed or worked hard like the good old rb20, now the redtop is back in my VL plus its a gts-r motor so i didnt want to get rid of it as these are rare