That particular 066 flat top was a build I did back in the 90`s when porting on here was all the rage, the cylinder has been shaved and running 18 -19 thou squish with just a bit of squish ring shaved out of the head to reduce the combustion area, then given the full port timing, opening up of the exhaust redirect the incoming charge through the uppers, lots of grinding in the runners up from the base to the uppers, piston windows opened up and a good bit of lightening on it. muffler opened up and port matched , carb bored and as much intake port and runner shaved as was feasible. The airfilter is a flat standard steel mesh so no restriction on air intake or at least little as possible, the sound it makes reminds me of my open airfilter V8`s 455 big block Firebird when the dual4`s opened wide.The old module on it has lost its retard for start function and I could easily put a new module on it as I have several sitting here but I like it the way it is, it punishes one a bit just like 3500 lb return springs on the ole standard clutch McLeod Purple clutch setups in the 70`s, not a good choice for city driving between stop lights.