Replacement engine / gearbox

When the inevitable happens is there a ready supply of replacement engines and transmissions , sensibly priced ! . We have a 172 cup,if the worst happened would a different engine be recommended for track days.
 
172 / 182 engines are around £500 on ebay depending on mileage or you could splash about a grand and try fitting a 197 lump in there as some have done in the past although not heard how long they lasted as it's a bugger to fit