74 225 slant 6 options

so.... Im in the process of configuring what I want to do with this engine.. Im not planning on ever replacing it with anything else (all numbers in this car match and im quite happy with the fuel economy it provides me as a daily driver) but would like to know what upgrade options there are avaliable for this.. Ive heard rumours about being able to upgrade its hp fair bit with the a few replacement parts here and there ( a whopping 105 hp currently, damned emissions anyways)... I will be pulling the engine for cleaning/painting and head gasket repair in the future so would like to know what I could do while the slant is out and able to be torn apart..

Thanks again! :D