Plug gap for this truck will be.062 for gas and for LPG.045. You will find that GM engines come from factory set up for gas and not LPG. Here in Canada gas trucks are uncommon , LPG is widely used.

thats the gap for the plugs
youre right this has no points

ive had those kick back in mitsus
i did see one break the mounting ears off too

using matchbooks, business cards etc to set points doesnt work because the "dwell" (or hang-time) is different for four, six, or eight-cylinder engines.

i adjust to spec for the specific engine then fine tune by checking dwell while running.

if memory serves that's the GM vortec with platinum plugs and HEI with external coil and module hence the big gap. no points---but most likely an ignition time delay module (delays +12V to the coil to ensure full engagement of the starter in case of kickback) which is always the first place i look if +12V to the coil is absent...

dont disable the relay or kickback could destroy the starter and possibly the mounting ears on the block itself... hyster had a servicegram on that issue

im seeing for a D004 with the 4.3 liter v6 is.062"
pretty big gap


as far as using a "matchbook" to set points
i cant tell you how many times i had to come in and readjust points with a feeler gauge after someone had set them that way

to know its right makes me feel better when im cleaning up my tools

i always double check the points and plugs gap even when plugs are pre-gapped

Tell your guy to fit it will be ok to be honest about it i cant remember the last time i set a gap on a spark plug i have never had any problems with i mind years ago when i started out on forklifts when u used to get points in a distrubuter and i asked the same question about what to set the gap at and i got told to use the cardboard the points came in as the gap to adjust it to i laughed i thought the guy was being silly but i tried it and the truck started ok and the engine run fine and thats true.