DEVELOPERS have begun unveiling their building plans for the four sites picked up at Tuesday's government land auction. Amazing Wave International, a 50-50 joint venture between Emperor International Holdings and Emperor Group chairman Yeung Sau-shing, said it planned to build two 19-storey luxury residential blocks on the site it bought in Cox's Road, opposite Kowloon Cricket Club. The company paid a record price of $360 million for the 15,000 square foot site, formerly home to the Norwegian Seamen's Mission. Amazing Wave said the luxury units were expected to range in size from 1,300 sq ft to 2,000 sq ft and carry a price tag of about $5,000 per sq ft. The development will have a total floor area of 94,600 sq ft, with two towers built above a two-storey car park. Amazing Wave hopes to begin laying the foundations by the summer and has scheduled the redevelopment for completion in early 1995. Mr Tony Tse, Emperor's property department senior general manager, said: ''The lot is situated in an excellent location, easily accessible by all modes of transport and surrounded by green belts. ''The availability of land for luxury residential projects in Kowloon is very limited,'' he said. ''In view of this, we are confident this project will generate satisfactory profits for our group.'' Some analysts have questioned how the developer can make reasonable profits considering the exceptionally high price paid for the lot. But Amazing Wave is confident that the development will sell well, partly because of the good views from it of the neighbouring cricket club. Nan Fung says it intends to begin work immediately on developing the $705 million site it bought in San Po Kong, near Kai Tak airport. A representative said that, although precise details of the development were not yet known, it would develop the site to its full potential with a mixed commercial and residential development on the 33,293 sq ft site, earmarked for non-industrial use. Nan Fung hoped the project would be completed within three years. The site carries the unusual stipulation that a refuse collection point and a public library must be included in the development. Sun Hung Kai Properties has kept tight-lipped about its plans for the 113,021 sq ft residential plot it bought in Yuen Long. The site has a plot ratio of three, which equates to a maximum gross floor area of 339,063 sq ft. The manufacturer which bought a 9,860 sq ft industrial site in Kwai Chung has also not yet announced its plans. The site is unusual in that up to 75 per cent can be used for ancillary offices, a considerably higher proportion than normally allowed.