Well, the "good news" is thats not normal, which means it's fixable.
A hot restart should be in the 2 second range for the GM 4.3L.
Where in the US are you located?
My speculation is you have a regulator gummed up with "heavy ends". It's a tar like substance that makes the internals of the regulator act slowly.
If you're willing, I'd like to send you a regulator "repair" kit. Not sure if it's been released by Doosan US yet, but if youre game for it I'll send it to you. Basically you remove the regulator, take it apart, clean the tar out with carb cleaner and put it back together with the new gaskets in the kit.