The problem with that is that 1) the screws will be going back into the end grain of the dowels (which doesn't hold as well), and 2) most dowels are pretty soft wood anyway. It's a good technique for a lot of things, but I don't like it very well for an application like neck screws with that much tension on them.
Some alternatives would be to use a stronger filler material (maybe epoxy), switch to larger diameter screws, or to put thread inserts in the neck.
This has been covered a couple of times and some of you might know what I’m about to say:
Drill out the surrounding wood. Make your own hardwood dowels (I have described the technique for this a couple of times in similar threads, use the search function) glue in and re-drill the holes.
I have done this like a dozen of times and there ha e been no problem with the screws chewing up the new wood just because the go into end grain.
Any other “easy" fix is as begging for more problems. The toothpick method is the second best and will work for long times. Epoxy, wood putty, titebond and similar substances are NOT formulated to do what you are trying to do. It might hold up for a while, but it will fail over time and it will not let you tighten the screws very hard
And as Mickey says:
If you tighten the bolts that hard you should consider threaded steel inserts and steel machine bolts instead.
EDIT: I did the search for you:
http://projectguitar.ibforums.com/index.ph...ill,and,redrill