If it's an MTB-style SPD pedal with a 2-bolt cleat mount I wouldn't go down the SPD route at all. Time ATAC Aliums are way more reliable and fairly easy on the wallet.
Simple spring mechanism, serviceable bearings and the cleats last for yonks. Been using them for 'cross for a decade now (in fact I think my original pair of Aliums from 2002-ish might still be on my touring bike....)!
David