I’m working on my GTS, installing some 440Source heads, changing camshaft, getting rid of the leaking beat up 187 pan for an 893 pan, a few other things. I have the correct driver’s side engine mount bracket, but the engine that is in it is a 75 C-body 440 and it is not drilled by the oil pump for the M-code bracket to bolt to, so it’s been using a 383 mount. Correct 440 manifolds, original power train is long gone. My brain could be fading but, why could they not use the 383 mount bracket? I know that the factory M-code blocks don’t have the mounting holes like the 383 did but why not? The 383 mount has been working fine for at least 10 years. First photo is a (stolen from the net) factory 440, second (also stolen) is a factory 383.