If you've been riding properly most of your base work training for the 94.7 was done in small gears which got your legs used to spinning quickly. Does your bike computer measure cadence? You should be cycling at least at 90rpm on a flat road. A bit less on the hills. If not, not all is lost as you can develop some speed.
A few tips:
• In the next 6 weeks do lots of endurance base work spinning around in your small chainring everywhere except downhills.
• You can average nearly 40 without ever going to the big chainring when you get the hang of it. A 39-15/14/13 ratio goes a long way

• When you change into a bigger gear make sure your legs are just about "spinning out" in your current gear.
• When there is a short climb or rolling hills, keep your legs spinning for as long as possible in your current gear but change to one gear lighter before you start losing any leg speed. (you don't need to be going really hard to do this either initially while doing base work)
• Keep the legs going over the top of the hill.
• Concentrate on a smooth pedal stroke
A speed workout that I do indoors on the rollers:
(Because the resistance in minimal I start in the big chainring.)
- Warm up for 10 minutes with legs spinning comfortably.
- Increase the resistance by changing up a gear and increasing cadence (sometimes go as high as 140rpm) for 2 minutes
- keep the cadence consistently high as you go through the gears staying 2 minutes in each (don't pay any attention to HR - it should be high)
- go back down the "ladder" of gears staying in each for 30 seconds or so
- start again
There are many variations such as going up 2 then one back etc. Make it up as you go. You can also do this on the road but it's more difficult to with external factors.