Just pop out the smoggers and weigh them, then weigh the proposed 10-1's, the 10-1's should b heaviest,reduce them in weight to the smoggers weight, but 1st check comp dist b-4 u invest much time and effort u may b swapping in the same thing..chk how far down the hole the smoggers are,and the comp distance of new ones to determine how far down in hole new ones will be, then u need to know what cc ur heads r to determine comp ratio and u prob aint gonna see 10-1 maybe 9.3 or so but way better than 7.8...I had a early 70's blk advertised as 10.5-1 that when calculated the cc's of heads and how far down in the hole came out to be a true 9.69 comp ratio..only way to know 4 sure is chk it