Digital Multiplexer T74LS151B1 on interrupt

Hello,

I ran out of pins on my arduino and realised I am in dire need of a multiplexer. After some research I decided on this digital one: T74LS151B1 as it just happened to be on offer on ebay, 5 pc alltogether.

There are basically two things I would like to do with them:

First just hook up 7 toggle switches to it, I've done the wiring but am slightly confused by the MUX151 tutorial in the playground. For once I don't understand the part about the strobechannel. Anyway, I will try to push through with it and eventually it will start working, I hope. In another thread I have also read that one should put some resistors on the 5V input of the mux151, is that necessary?

The other thing I am intending to deal with once I get the basic setup and code right is to hook up 8 rotary encoders via one of my MUXes. I got one of the 2-bit grayscale encoders working fine (without a mux) on an interrupt and now i'm wondering whether I can run all 8 through the one interrupt channel. I'm using both a diecimilla and a mega for this project but would like to use up to 20 or so encoders with the mega plus their inbuilt push buttons so would need quite a few interrupt inputs.

This project is for my masterthesis, a digital controller for sounds and visuals using pings as the main inputs plus a dozen of pots, encoders, faders a display and whatnot. I guess I could run the 7 pings i am using via a mux as well to save even more pings, well let's see, they're working fine as they are right now so no need to rock the boat just yet, thank you in advance for replying,

Best, Karl