I'm seriously thinking of upgrading my 364 with either an MSD or HEI distributor. I have seen both for sale on ebay, the HEI ones seem to be a lot cheaper than the MSD, plus they come as a kit with a coil and spark leads etc. Can anyone tell me if there is a significant quality difference between the two? I have also seen the pertronix distributors too, that seem to be priced somewhere between the Hei and MSD units. Are they easy to install?