I don't understand their work methods. Or rather, to quote Captain Willard, "I see no method at all...". He's slapping Hammerite on that RH inner wing whilst the rest of the car hasn't even been stripped and/or investigated.
The only thing keeping the whole front end of the car together at the moment is the engine crossmember, and the engine is still in the car (???). The state of those air tubes (which are - in effect - upper chassis rails) says that the whole of both lower chassis rails and probably the double-skinned sections at the bottom of the strut towers needs replacing. He's talking about the LH chassis rail just needing some patches (???!!!).
I watched one of the other videos where the younger guy is working on the forward end of the RH sill, peeling away the outer part of a double-skinned layer until he gets a third of the way down the car, and then stopping. That outer sill should only be single-skinned, so it seems likely that the car has in the dim and distant past been fitted with 'cover sills', leaving the original sill outer in place. They need to replace the whole thing, probably on both sides.
In the first video in the series, the older guy says he thinks it used to be "...a race car or a drift car." Amazing how many people think that. I guess an ordinary car that falls into disrepair across multiple owners, receiving make-do-and-mend repairs just to get it through another MOT year after year, and then falling into the hands of a 'Gunnar' who gathers some parts (new door handles and a set of 240Z Hitachi carbs) but then turns the car into a dumpster is just not romantic enough. So, "Race car"...
The end result here can't hope to be anything more than another lash-up. What's the point?