I definitely wouldn't try to draw the wood together with screws (I'll explain why later).
I'm assuming from your descriptions that the door is composed of stiles (vertical components), rails (horizontal components) and panels. It sounds like it's a beefy door with the crack in a wide stile (lock side or hinge side?). Being as old (and as dry) as its age suggests, if you split the crack completely, as was suggested, you'll likely get uneven splintering and irregular separation of the wood fibers along the longitudinal axis of the grain. One would hope that you could apply glue and piece it back together like two pieces of a puzzle, but trust me, it won't work. (Don't ask me how I know this! lol)
I'd recommend gluing it together. If properly glued with the adhesives available today, the joint will be stronger at the glue line than the natural resins that bond the fibers of the wood. The trick is to "wet" both sides of the crack with glue as completely as possible and to apply sufficient clamping pressure. It shouldn't be too difficult.
It would be best to remove the door and lay it across saw horses... or across some 2x4's on the floor on edge.
Buy a cheap syringe at the drug store. Buy a small paste brush at Home Depot or Lowes (it has short, stiff bristles and is used to apply flux for soldering) and purchase a good quality, exterior grade glue (TiteBond). You can thin the glue with some water (experiment so that you thin it only as much as is necessary to make it flow through the syringe needle). Have enough clamps on hand to apply them 6" - 8" apart for the length of the crack.
Gently pry the crack open with a screw driver, if you can, so as to get the brush into the crack and spread the glue onto both surfaces. If you feel that prying will increase the crack, stop! Use the syringe to flood glue into the crack as far down as you can (gravity will pull the glue lower into the crevice... so give it a minute). Plenty of glue is good. Whatever squeezes out after clamping is easily cleaned up. Once you've got as much glue into the joint as you can, apply the clamps. A thin strip of wood (3/4") between the clamps and the door edge will protect the door edges from clamp damage and will also help to distribute the clamping forces. Alternate the clamps on each face of the door to prevent the door from bowing under pressure from the clamps (one on the outside, next on the inside, next on the outside, next on the inside... and so on). Wipe up any glue squeeze out and leave everything for at least four hours to ensure sufficient initial cure ('cuz some glue has been thinned).
Remove the clamps, close the door (gently 'cuz it'll need 24 hours to reach it's strongest bond), stand back and admire your handy work!
Why not to screw?
You stated that the crack is about 8" from the edge of the door. You'd have to bore a pilot hole into the edge of the door about 4" past the crack, or
8"+ 4" = 12", to have sufficient depth for the threaded part of the screw to bite. You'd need about 4" from under the screw head to the crack, for enough wood mass under the screw head to bear pressure onto the crack. You'd have to counter bore 4" into the hole for the screw head to enter the hole unrestricted. Eight inch screws are available (not readily though) but they'd be too weak at that length and would likely snap if under #14 gauge. You'd need a six inch #3 Phillips or Robertson driver bit to reach far enough into the hole, and the bit would likely "cam" out of the screw head under the forces you'd be applying (if you round out the cavity in the screw head when it's buried in the door, you'll never get it out!)
And lastly, but most importantly, the forces required to draw the crack together would be greater than the resistance applied by the screw head, and the threads would likely just draw the screw deeper into the hole without completely closing the gap (if the screws don't break!). Been there... done d'at. Don't do it.
When the weather permits... refinish the door. The hot summer heat (and cooler interior) and the cold winter air (and warmer interior) create expansion and contraction forces that constantly flex a wooden door (worse if exposed to direct sun). There's also usually a humidity differential on both sides of the wooden door during the changing seasons. All these factors contribute to wood fatigue... hence the crack. If soundly repaired... and properly refinished... it should last another generation (with proper maintenance).
Thanks for enduring this lengthy post. I hope I've been able to help you salvage and restore a venerable old soul, that's been hanging around longer than you and me (pun intended)!
Good luck.
Michael