im looking to switch my trebles on my cranks to the mustad triple grips...

my question is...what size hooks are on most med depth & rat-l-trap type lures?

my choices are sizes 4,6 & 8...i dont really have to many larger cranks,just your typical 1/2 oz. traps & 4-6 ft deep cranks

Most of the trebles I use are #4 and #6, with a few #8s and an occasional #2. A standard 1/2 oz. Rat-L-Trap has a #4 on the belly and a #6 on the rear.

You really should stock 2's, 4's, and 6's, but 4's are what you are looking for to replace 1/2oz trap hooks.  I use Daiichi 4x red trebles, and buy them in 100pks from Cabelas to save money.  

I use Owner hooks on my traps , a #4 on the front and a #6 on the rear.