Prepping the engine bay before paint turned out to be "loads of fun". There was about a 1/4" of crud and mank (that's a technical term) coating the inner fenders and firewall. I used a combination of kerosene and diesel (sprayed on) and various scrapers to remove it. (I wish I'd took pictures) I was left with a very hard "stippled" coating on the inner fenders, I don't know if this is factory but it would budge, not even with laquer thinners, so I left it on.
Once all the crud had been scraped off I washed the inner fenders with a rag soaked in gasoline. This was followed by a good sanding. I used a Mipa self etching primer which is also a filler/surfacer, it has great adhesion, leaves a nice smooth surface and can be painted over without additional prep. I used my touch-up gun as it's easier to use in confined spaces and being HVLP you get very little overspray.
The paint code for my truck is 528 which is fawn.
I painted the inside of the cab at the same time (it was gold

) which is why the tag is not attached.
Like many old trucks mine has been painted in the past, so there's no guarantee it's still the correct colour. I removed the panel below the windshield and took it to my local paint suppliers and they matched it to a BS colour
No not that kind of BS, a British Standard colour, BS 08C31. The match is very good. It ended up taking 2 weekends, although most of that was prep, but I was pleased with the results, especially when compared to the earlier pictures in this thread.