Idle screws are on all 6 bbls, front & rear are in the base , front two you say are siezed up .so that is part of the problem .
what is the idle vacuum in gear & power valve rating .
often the air bleeds are a problem & inserting a small wire into the outer idle bleeds really helps as you...
The 74 usually had a carbon canister for emissions & the shroud probably made clearance for that so the 73 will fit but you probably need to remove the carbon canister .
The way I look at most things is it is not working now so how much worse can it be if i take it apart & try to repair it , if it still doesn't work oh well ...
Basically impossible , the bows & sail panels will not work with the smaller SE window , I suppose ou could use the SE sail panels with a regular headliner & bows to make it work .All SE I have seen have the console as part of the SE pkg , no separate code for it .
All V8 K frames are similar & will work except for the Hemi .
The 318 K frame will not have the skid plate but that can be welded on if you want it later so with the correct mounts for the 440 it will drop in .