Ultimately don't worry about the suspension over much at this point. As long as you can fit the tire size you want now, you can fine-tune the height later at minimal extra cost.
If you're doing a restoration that's going to cost you easily $30k in new parts, another $200-$500 is actually kind of minimal. And on top of any new springs you purchase to fit your desired tires, you can re-sell the stuff you have now as long as it's in good shape.
It sounds like your springs are new-ish now, so selling them on later is not that hard of a deal and will recoup some of your added expenses to get taller springs if you need them.
Back to your other question about height, in the front stock height is considered to be approx. 7" between the top of the axle tube and the bottom of the frame rail. You can still measure how it sits now to see what you are at without the engine. It won't tell you how much lift you will have when it's at full weight, but it will tell you what you're sitting at right now.
If they are modern variable rate coils, you will probably be sitting taller than final height by a couple of inches. If they are old-school Rancho coils however, you might be sitting at close to the final ride height even empty! Maybe an inch or so?
They are 3" coils but are very stiff (they're made for full size Ford trucks) so may not have as much sag when weighted down.
But Jim had the best advice for sure. ABSOLUTELY DO NOT BUY YOUR FINAL TIRES YET!!!
Can't stress enough that life gets in the way of 95% of us when doing a long-term project. Only a few people can start and finish a vehicle restore in a year or less. Maybe you're one of those with that kind of focus and a family that leaves you alone in the shop. But if you're not you might be driving on outdated tires ten years from now when you finally get it road worthy!
Definitely something to think about.
Paul
