I'm pretty sure this has been discussed before (can't imagine it hasn't) but I'm trying to detail a minimal method of converting a Dragon 32 PAL machine to output NTSC. I've (sort of) done this on my reproduction boards but want to check the theory of the process with the collective
Step 1 - Rewire to use raw !HS instead of !NHS
Step 2 - Rewire to use raw VCLK instead of stalling VCLK for padding lines
Step 3 - Remove IC11 (analog multiplexer) and wire across pins to use raw Luma and PhiA
Step 4 - Remove XL1 and wire VCLK to IC9 pin 18
The result is a 60Hz signal, no padding and just direct signals from the VDG to the video encoder/modulator at IC9
The minimal process involves lifting (or cutting a few chip legs), removing one chip and running a bodge wire from IC12 pin 38 to IC15 pin 9 and another from IC15 pin 7 to IC9 pin 18.
This renders a long list of chips redundant and if you want to do a more thorough job you could physically remove all those chips instead of just lifting a few legs. I don't believe any traces need cutting so this should be completely reversable, or even switchable if you wanted to go the extra mile.
The only flaw I can see is the timing any timing tied to HS and FS