Hi Malscar,
Excellent choice, but take care on spoilers starting from Procar version, there are different on M1 rally cars.
you have to reshape the bottom of the front spoiler and the bottom of wheel arches to get maximum accuracy.
best thing would be to refer to 1/43 Robustelli TK's building instructions.
if you need it I can scan and send it to you.
if you need a picture of the racing engine, I have one, too.
This car is my favorite BMW and it was a so incredible as unexpected one, especially its sound was fabulous !
i only have one in 1/43 scale that costed me 45 hours of building and detailing !!
let me know if I can help with pics or informations !
Phil