[ovilla]

Don't worry about a slight mismatch. I swapped out my 75' heat exchangers for a 74' SSI unit and also installed a new 74' Bursch and had the same mismatch problem. First, I made sure that I filed across both HE's evenly with a big "bastard" file (actual name of the Sears file). Then I bolted the HE's to the heads and tightened one end to the new Bursch. I then used a really long threaded bolt and nut to get the "mismatch" to line up temporarily so that I could install the other two bolts and then replace the long threaded bolt. Anyway, you'll find that the HE's will warp after some use as the heat brings them into alignment. Next time you take them off they should line up better. Finally, if you did a retrofit from a 75' or 76' to an earlier exhaust set up (70'-74'), you will need to use the earlier muffler hanging bracket as well.