1 1/4 is bigger than 30mm so you cannot use reducers.
Most spindle tooling is available in both 30mm and 1 1/4
The other way of doing it, is to see if you local saw doctor can open up the 30mm bore of your blocks to 1 1/4, or they may be able to recommend an engineering firm who can.
If you are very lucky you may be able to pick up a second hand 30mm spindle, I know Wadkin made them for their machines and it is possible Wilson did too.
Tom