i have completed a hydro to solid conversion with my 5K. its not that hard, if you are going to be putting the 4K head on it, just get some chev v8 solid lifters (also used in the 253 Holden V8) and then with the 4K head you need to use datsun A12 pushrods cause the 5K ones become too long.
i have heard of people ripping the guts out of the hydro lifter and getting longer pushrods to make them a solid lifter.
and i'm pretty sure, don't quote me on this, that the cams are different.