Toyota Camry 1991: Is an high kilometre engine suitable for gas conversion?

I have an SV22 four-cylinder Toyota Camry with 260,00-plus km on the original engine and I was thinking of having it converted and taking advantage of the remaining $1500 government subsidy. Is it a good idea to do this so late in the life of an elderly engine? Are there any issues likely to manifest themselves where an engine has spent all of its existing life on ULP? It's an older car now and I'm not sure spending thousands have the engine done up really makes sense.