The Sprint originally came in either 3 or 7 speed hub gear versions, but you could convert to the 8 speed hub gear without problems.
To convert to deraileur you'll need an add-on rear mechanism hanger which Shimano make. This can be difficult to get hold of but St Johns Cycles (SJS) have normally stocked them. This is a photo of it, it sits in the rear spindle slots in the frame:
The conversion to derailleur is slightly more difficult since you need to choose all the bits to be compatible and will need a complete new rear wheel with a cassette hub mounting for the rear sprocket set. The 8 speed hub gear conversion should be very straight forward if you get a dealer to build the hub into a rim for you.
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