I want to put a 26" wheel on my night train how much rake do I need?

 

I'd guess at least a 5 degree. But the answer you need to be looking for is getting your trail right. You may need a 7 degree just to get the front back down enough so your trail isn't out

 

If the bike was raked before I bought it how can I tell how much it's raked?

 

Has it got the stock tress on it or aftermarket ones?
Be easier if you just google how to calculate trail, then me trying to right it all out