I used the plans from Rocket Engineer on Reef Central to build a basic stand for a standard 125G tank a few years ago, very sturdy and you can finish the exterior any way you want.
The link is Rocket Engineers DIY Stand posts #3, #4 and #5 for the instructions.
Pics to my DIY stand are Here at post #7
Measure the tank first. While a standard 125g is technically 72in the trim adds just over an inch for some brands. I add a 1/4(0.25)in. For wiggle room to the final length of my rack boards.ok thanks went to the timber yard today they said the can cut the measurements I want they aslo asked me if I wanted hard wood or soft wood, they also said they have 2 by 4 and also 2 by 6 . Would it be a good idea to make the tand slightly longer than the tank say 75 inch for a 72 inch tank.