Insurance companies are a thorn in our side. Specialty companies will cover your ride for whatever reasonable value you determine (many will require an appraisal for any thing over about $10,000). But they won't cover its use as a daily driver, and many have annual mileage limits. They are usually reasonably priced. Covering a modified vehicle will depend on how its been modified.

Normal car insurance will cover you for up to a specified amount under a "classic coverage", but be sure you get "an agreed coverage amount". A stated amount doesn't mean squat, they will give to what they think its worth if it gets wrecked (which won't be anywhere near what you thought you had it covered for). Most of those will not allow daily driving, and they really don't like modifications from original.

The only option that allows for daily driving is your normal insurance, but full coverage on an old car or truck is a waste of money, they won't pay out much based on its value compared to other cars of its age, compared to the value of a new car. Normal insurance companies don't like old cars & trucks, there are not enough "safety" features, and they can't charge you enough to get rich.

I carry only liability insurance on my coupe. If it gets wrecked, drag it home and I will rebuild it as I can.

50s trucks were rated for the job at hand, 1/2 ton, 3/4 ton, 1 ton and on, up to semi tractors. The designated rating was literal, a 1 ton had the capacity to haul/or pull a 2,000 lbs load, however modifications could be made to add additional load, within reason. I believe you had to get in to the 60s before load rating no longer reflected the actual payload capacity. Gene