As I see it, if you have already oiled the wood with Tru-Oil you've got a problem.
Normally I would say that you could stain the two pieces (butt and forend) with a diluted water base stain and then apply a few extra coats to the lighter forestock so they end up matching but if you have applied any oil type finish the wood won't take the water base stain without some work.
What you really want is raw wood to stain.
Hopefully others will chime in on this one, but I think I would want to "kill" the oil you've applied.
Where thinners would just make the oil penetrate deeper you need something that actually breaks down the oil to reduce it's water resistance.
Among the things I can think of that will do this are MEK, ACETONE, Lacquer Thinner, Paint remover?? and Disk Brake Cleaner.
The Disk brake cleaner is not explosive like the MEK, Lacquer Thinner or ACETONE but it isn't good to breath it so it should be used in a very well ventilated area.
Before you try any of these, I would urge you to put some Tru-Oil on some other piece of wood, let it harden and then try them.
Another idea would be to try staining the oiled wood with something like Minwax Oil based stain.
Normally I don't like oil base stains but if the Tru-Oil hasn't totally sealed the wood fibers, it might work. Then again, it may make a Mell of a Hess.
Good Luck to you.
PS: I know this isn't the time to say this, but to ALL of you folks out there thinking about refinishing your stocks, after they are sanded and ready for the finish FIRST, go outside in the sun. Apply some water to the surfaces of the wood pieces and take a good hard look at them.
The color and brightness of the wet wood is what you'll get if you don't stain the wood before applying the final finishes.
If it needs staining, do it before you start the oiling processes.
Zonie (Jim)