The basic cable & adapter set I'd recommend for covering all likely scenarios when your recorder has an 1/8" mini input is as follows:
- 2x Female XLR>1/8" mini
- set of RCA cables (will cover a sbd with RCA outputs or for 1/4" outputs with adapters below)
- 2x RCA>1/4" mono adapters (for when sbd has 1/4" outputs)
- RCA>1/8"mini adapter
Personally I think every taping bag should have all of this stuff in it, not only for sbd feeds but for patching in/out or other curveballs that come along. One piece of advice I have for sbd feed cables is to get them adequate long so you can set up your gear out of the way of the FOH engineer - every sbd is different and sometimes I need to put my stuff 15-20' away, so be prepared so you can stay out of their hair as needed. In my experience XLR is by far the most common output, but the others do happen sporadically. Length is pretty much a non-issue for XLR cables, so I'd recommend something like 20' cables and personally I always carry a few sets of these so I can run from far away if needed. Get a roll of gaffers tape for your bag as well to tape things down (don't use anything other than gaffers tape and always clean up your mess or you'll make enemies of the FOH engineer very quickly).
As far as using a D8 or any other recording device with an 1/8" mini input, realize this isn't ideal to run a hotter balanced feed into a small recorder like this and brickwalling is distinctly possible. If you want a sbd patch kit to be dialed out, I'd also recommend a set of -10db XLR attenuators that you put inline on the XLR cables to drop the incoming signal. You're better off to get the soundman to adjust the feed as needed from the sbd and not use attenuators, but quite often the last thing a soundman needs early on in a show is a frantic taper wanting his feed dropped, so if you percieve this to possibly be a problem, use the attenuators and you should be fine. The old rule of thumb on brickwalling with the small SOny portable DATs is if you need to set the level knob to <5 to get the levels where you want them, the feed is too hot and you need to turn the feed down until the level knob is at a position >=5. As always with brickwalling, don't assume that because the levels display where you want them that the recording won't have some distortion - the brickwalling occurs in the recorders circuitry before it gets to the record levels, so it's all a matter of how hot the incoming signal is.