copper is a pain and a very old school fix--yea it seals compression as long as you have the o ring but they leak water like ...well...they will always leak water. A MLS will seal like a bank vault IF the surfaces are smooth per the MLS instructions -- that means SMOOTH. You already have the groves--NO need for reciever grooves in the heads unless you have a full blown funny car engine. Put the correct diameter wire back in--have a pro shop do that --goop up your new coppers with RTV around all the water holes or...surface the block and heads to MLS specs and then remember to spray the MLS gaskets with Holomar SPRAY ( about $50 a can) or...put a 1009 Fel pro on it at about $70 a pair and run the heck out of it trouble free--they will only fail between cyl's --I have run 15:1 alky with Fel Pro 1009's and they lasted all season--I have run them on blocks that had old o rings--then they last about 30-50 runs AND seal like a vault. Just my 2 cents worth