[madmaxx]

The most demanding service in your engine is the valve train. specifically the lifters follwed by the cam followed by the rocker arm followed by the valve's. As far as the cylinders and pistons as long as you are running between 180f and 212 f they should last 100K miles or more. Depends if you boil gas out of the carb when you shut it down which washes your cylinder walls when you start up in addition to stinking the place up. see my phenolic spacer recommendation. Also if you are below 180f the cylinder and piston are not concentric and you will also get fuel dilution. I would have no heartburn replacing lifters at 20k miles. I bet the lifters you get are either comp cams or ford racing. i would prefer the ford racing. Jegs has them about $200 for a set.

A billet cam is usually suited for solid rollers which see extreme valve spring pressures so as long as there is not a defect in manufacturing and you arent floating valves the cam should also last 100k miles or more.

NOTE in a spf to run a 180f on coolant temps you need a 195F thermostat. A 180F will run about 166F. A thermostat opens at it set point but doesnt fully closes until 15F below it set point!!!!! The spf coolant system is so fantastic that it cools the engine incredibly well with very little flow. In fact i had a thermostat once that always had some flow i could never get the car past 150F in the winter!!!!! I use the cheapest one they make and it works perfect. Even in houston in the summer with 195 thermostat my coolant fans rarely come on, in fact I unplugged one because it would come on for 5 seconds and shutoff.