"If it is a specific factory produced part, that is offered on another model of their gun, then it is legal to replace the part with the gun you have, with the part from a gun of a different model.
Example, a Glock model 17 does not come from the factory with an extended mag release, but a model 35 does, both are legal in Production, so the interchange of the part is legal as well.
Sorry for any confusion and I hope that this explains things better for
Skunkabilly..you should be ok...the above is an email from Amidon on an ext mag release that is offered the 34/35 glock..and his statement is that it would be ok to install the part on a 17 as it is a factory part..
so with that logic..the D spring should be a go, and the novak sights should be a go as they are on the E2..I wouldn't worry about them being night sights as giving you any decided advantage..