Go with the 4k, theyll rev harder than the 5k and put up with a lot of abuse! Go basic reco on what youve already got, rings and bearings,
rollmaster double row timing chain kit, and modify the oil pump, new waterpump n gaskets etc, thats all for the bottom end!For camshaft grinding
try kelford cams in nerang go for a good bit of duration to get the engine revving to around 7k as thatll be plenty without balancing rod bolts etc,
3k bigport cyl head (welsh plug type) if ya can find one lol, double valve springs and a bit of a shave to bump up the compression, run your
manifold and su carbs a nice set of tuned length extractors and electronic dizzy conversion. Should be a fun little critter then, ps build it yourself with
a workshop manual its like meccano when you were a kiddie..... hope this helps.