I didnt understand well my friend loaded, sorry
I have an idea, not sure if you could do it.
If you have a number set, for example 1000 GGTS, take orders until you reach 1000, then they go to production.
If 1000 take 2 months to produce the wait time would be: Once goal of 1000 is met +2 months.
A counter showing how many have been ordered could be used by you and customers. People wanting to be 100% sure they get one would order right at the beginning. People who need to save a bit more or don't want their funds tied up as long could risk it and try to get in on tail end of batch.
For each item offered you could list the Magic Number for production to begin and the length of time production takes. I don't know the demand for the differrent items or the quantity where a price break occurs but I'm sure you could figure both out pretty easily.
It wouldn't take much communication on your end after it starts, as long as the production time numbers are solid and the order numbers are kept up to date everybody could see at a glance where things stand.