I got lucky,and a friend I did a small job for had a Elderbrock 2four set.Which he sold to me dirt cheap.How can I find out what mods need to be made to my motor for this setup to work.He reconminded changing the heads for better air flow.But he not sure of the size of cam that would work with this. It has 2 500 cfm.s carbs.He had this setup on a zz-4 motor and it ran nice.he took it off the motor when he sold it,so I know there wasn't any problems with it.I not looking to build a race car, more of the wow factor is what I am looking for

ignition, looks like you have the headers, heads, maybe a set of Edelbrock RPM heads,  talk to Edelbrock they have head and cam combo's  tell them what you have in mind, they will fix you up, maybe get a set of heads with smaller combustion chambers than you have now that will rise your compression ratio from 8.5 to 9.5 to 1, 10 on the street is about the limit, don't know how many miles your motor has on it but when you put new heads on a older motor it can put more presser on the older rings, I think if I did a motor I would start with a 425 hp 383 GMP short block, RPM or AFR heads,  solid roller cam, RPM air gap with a 750 CFM... good luck....BTW.., make sure to run Red Line fuel system cleaner with the 2x4's if you don't use the second carb alot, it will varnish up on ya if you don't use it alot. anips2009-07-19 19:31:26

Ignition would be a factor, 1975 was the start of the HEI distributor, and, from personal experience, it will not fit onto a 2x4 setup,  not enough room from the rear carb to the distributor... and as anips advised, a little higher compression than a stock L--48, as i had the pleasure of running 2 4's on the 76 for about 3 weeks, with a slighty above stock engine(L-48 with flat top pistons and a little more cam, about a 268 if i recall), and about the 3rd week in, i was burning as much oil as gas, killing mosquitos and any other flying critters behind me... ended up washing out at least 3 cylinders, breaking the rings and ring grooves on the pistons.... though, i was using 2 625cfm carters.... sounded good at the time :)  just a little food for thought, might want to jet down the carbs a little, 1000cfm is a lot of gas.... for a stock motor that is... 

I agree with both of the above.  That is a lot of carburation for a stock engine.  If you are just doing it for looks, make sure it is professionally re-jetted and it will perform almost as well as your original Q-Jet.  If you are looking for performance, use a modern single four barrel and the upgrades mentioned above.  You can't go wrong with an integrated Edelbrock system.

Larry