crossover guitar.

I will try to keep this short if i can.

many years ago when i was about 10 my step father was a telephone installer for the PMG. T his is an Australian thing but it stands for Post Master General. it was the government bodu for postal services and telephone/telegraph services. 

not rlelevant on a tangent already...lol

He had to crawl under houses to retro fit telephone wires etc.  one day he came home with a guitar. It was a homemade thing and he made a wallhanging out of it by painting the back. not a good painting..lol

4 years later i inherit it when parents split and he went back to England. 

i sanded it down and strung it with nylon strings because it had a classical style bridge. it had had steel strings on it and warped the top. i sanded the bridge to compensate staines it a red cedar type colour and did a poly finish... remember i was only 14. 

i played that guitar for over 25 years on and off i loved it. .

so basically i want to recreate it. smaller body and a narrow neck 46 ish mm would be good under the 1"7/8 freedom unit mark.  and a scale of 615mm or around 24.2" 

without buying a new guitar can i put nylon strings on a steel string guitar ? do i need to chanbe the bridge first?  do i just build myself a stick in a box 6 string with nylon strings? looking for the options and short commings of this idea? could i get a cheap second hand classical guitar and reshape the neck to a bit narrower? i would possibly have to replace the fingerboard with one say 16" radius?

i think the cheapest crossover guitar i can buy in Australia is over $700 AUD.

the whole point is to be able to quietly play at night and not wake the missus up! plus the nostalgia for a guitar i lost 24 years ago.