[Miniwerks]

I am considering a 1967 912 Soft Window Targa with just under 72k original miles. Very dry, original car, light ivory, black leatherette. Matching gearbox but engine was replaced due to engine fire. The engine number is close in build date and just a few hundred miles on rebuild. Otherwise excellent condition, will post some photos. Correct date stamped wheels, tool kit, jack, original interior, wood steering wheel. My question is what affect a non-matching engine has on value? I have heard 10-20% but as high as 40%. The engine number in the car now is 740402 and has Webers.