1st get aero like others mentioned. Then work on heat stress during easy rides, working up to ~ 80%maxHR for 2-3 hours in a closed room with no fan at ~32C should do the trick. Be warned about heat stroke, this type of conditioning can be dangerous if done too quickly. IMO, TT's are mostly about mental toughness. Here's a tip to subdue some pain... find a playlist of inspirational songs, listen to them on every workout. During the TT start thinking about those songs and all those days of training will bring your through.
Regarding TT bike specificity: Start off by renting a TT bike for competitions. Once you get a TT rig, start by using the heat training days to get comfortable in the position you chose.
Periodically adjust your training and make sure to rest and recover between. 4-5wk Vo2max, 1.5 week rest, 3-4wk FTP. 1 workout then 2 days recovery heat training. repeat.
To increase vo2max, I like the Tmax approach http://www.pponline.co.uk/encyc/how-red-hot-interval-training-fires-up-performance-in-seasoned-cyclists-54
I have good results with a 15x1.5min@v02max power, 3min recovery between sets. first 5 intervals build up to Pmax, 5 at Pmax, then suffer through 5 more below Pmax.
For FTP I would try to replicate a TT as often as possible. After your normal warmup, 30min at 70%FTP then 30min at 85%FTP, then 10min at 100%, and finish it off with another 10min increasing power to whatever power you can hold.