Regulations questions- vehicle length and overhang

I have built a flatbed truck to haul cargo trailers for local company. Total truck length is 38' with a 26' 6" bed, my trailer is 27' (I'm just under 65'). I'm going to weld a lightweight 5th wheel head to my class V hitch to quailfy for stinger steer up to 75'.

My current arrangement, the trailer overhangs about 6". One of the reasons I set everything up this way was to load the trailer on my flatbed when I leave CA to avoid the 55mph towing speed.

In a commercial aspect, what would be the max overhang for my 38' truck? I see truck length limits of 40'. Can I have 4' overhang in the back for a total of 42' (38'+4'), or does the overhang count toward the 40' (38'+2')?

Seems to be a little abiguity. I understand when you're in the 75' configuration with a trailer, the 4' overhang is pretty standard, but as a straight truck I'm having trouble getting a firm answer.