Fish, I know exactly what you're feeling. Been there. But I'm staying with iron sights, beause I've learned a few things via experience in the woods, when the backgrounds are gray brush, when the sun is too bright, or the angle of light is wrong. It can be overcome. This past season, I was looking through peeps at a deer at dawn in the brush. Couldn't make him out at all through the peep, but I could see him plainly when I lowered the rifle. The fix was to move my head toward the peep hole, really pulling the gun it tight and moving my head forward, which in effect, made the peep hole "bigger," and there he was, plain as day.
Another problem with peeps is that at my age: a rear firesight is just too bright, and floods the hole with light and color to where I can't see the front sight clearly. The answer to that is firesight on the front only. It easy to focus on a firesight that's way the heck down at the other end of my barrel.
What works at ther range, will probably not work in the dappled light of the woods. Light is coming in from different angles in the woods, and a little larger hole is needed for the rear peep.
Of course, a scope will erase any sighting problems. You will always have a clear sight picture, it's magnified for better bullet placement, and you have only one item (the crosshairs) to center on the target. But is that really what you want with a 45-70? Maybe so, and that's okay, but not for me. I've been tempted, but have yet to give in.