the conversion is the old 'Maintrack' tandem Hunter (the resin piece has nose contour issues being based originally on the 'Matchbox' Hunter nose), currently Martin of the IPMS. Whatif sig is remastering it, i think another example is due soon from Cambell at 'Odds and Ordanance', an easy enough conversion tho just cutting and lengthening the forward fuselage and splicing in an extra canopy length :)
cheers, Joe