Bicycle Tutor

I have a Shogun road bike. About 18 years old. Still in good shape. Runs smoothly. Has downtube friction-hold shifters. In my old age, I no longer like the downtube shifters (too hard to reach) and want to change to friction stem shifters. (Have been told to stick with friction because indexed, though I would like them, have to match the gears, which is unlikely for my old system, so I am told.)
I have ordered a set of new friction stem shifters and two new cables. Does anyone anticipate any mounting or adjusting problems? Or, have suggestions? Right now, unless advised differently, I intend to leave the old downtube shifters in place to use as the cable race through which the cables slide on their journey up to the stem shifters, just above the downtube shifters. Appears to me that this setup will work.
Any advice or cautions?

It's possible you could use the old shifters as cable guides, but I suspect you'll have some trouble, particularly when turning the bars. The right way to do it is to get some of down tube cable stops (http://www.jensonusa.com/store/product/F...http://www.jensonusa.com/store/product/FR308Z06-Shimano+Housing+Stop.asp and run housing from the new shifters to where the old shifters were. There are a couple types of stops. The ones I linked to are made to go on a frame that has the posts for the frame shifters welded on. You can also get ones that clamp around the frame if you don't have posts. You can use either shifter or brake housing if you're doing friction.
Other than that, you should have no problems.
Note that to go index, you would probably just need to get a new freewheel to match the shifters. But there could be spacing problems on the rear wheel.