Surely it doesn't have s1 front calipers?
As they are xr3i sized on the s1 and very underpowered.
S2 discs are 260mm iirc,s1 and s2 drums are the same size I think.
Best setup without going for rear discs are 4x4 cosworth front discs and pads and escort mk4 van rear drums as they are huge.
I think you will be ok with the s1/2 brake flexis,they are prob the same anyway but if you're not certain measure your flexis and ask the seller the length of the flex is you want yo buy.