Well the ladder rack and modded headbolts are a one time thing really. Although the headbolts are stretch bolts, once you have the modded ones, they are generally reusable.
Once all the thermostat and ladder rack and all the other mods are done , headgasket failure is then a 1-2 hour job cost like £40?
I'm also trying to think of the last time i saw a K series with plastic dowls and im thinking they brought out the first (of many) modified headgaskets with metal dowls available from parts in about 2001 (ish). You must be gentle as hell on your engine! Seems the K series runs off TLC.