Well nobody proffered any advice on this post, so here's an update just in case anyone becomes interested in the future:
I replaced all 8 lifters tonight, then took a 60 mile, break-in, drive.
The old lifters (100K) had begun failing internally, but externally, the bases weren't worn enough to indicate any noteworthy cam wear. I was quite pleased to see this -- especially on an engine with this much mileage. The push rods were about as straight as one could hope for, but I bet I would have bent one eventually had I not corrected the lifter problem. Dang things cost about $3.50 each, and nobody has any in stock around here. I was hoping to grab a few to have on hand just in case I found a bent rod. I guess the most valuable tidbit from this is that even a 100K, 4 Banger, can go a looooooooong way without any wear (other than polish) on the camshaft!
There is no more "rat tat tat tat", I'm getting improved accelerations, and a nice, flat idle now. Based on my little peek inside the engine, I wouldn't be surprised to get another 100K out of her! No sludge that I could see. In fact, I was shocked that the engine is so clean inside after so many miles and previous owners! My local mechanic wanted $200.00 plus to change the lifters for me. They cost me less than $40.00 and only took about 2 hours to replace. Definitely worth the little bit of money and trouble to get many more miles out of my healthy lower end.
I had a number of folks tell me I'd DEFINITELY regret doing this on an older engine, (including my Haynes manual) but I think my biggest regret could have been deciding to listen to them instead of using my own common sense. While I'm mechanically inclined, I'm not an experienced auto mechanic, so I'm very happy I followed my own instincts on this one - otherwise I'd probably be spending thousands on a replacement engine instead of $45.00 for lifters, lube, and one special tool. *smiles*