The Serpent 733 can be upgraded by using a number of the new parts which are made for the 747, but actually also for all 733 cars.

Below 3 suggested levels to upgrade

Level 1 upgrade

804257 Geardiff uni 1/10 GP Smoother, easier assembly
http://www.serpent.com/product/804257

804281 Wishbone 747 RR LW medium (2) Improved geometry
http://www.serpent.com/product/804281

804129 Rear bracket alu narrow V1
http://serpent.com/product/804129

804282 Upright 747 (2) Improved geometry
http://www.serpent.com/product/804282

804283 Bumper 747 Larger, more steering
http://www.serpent.com/product/804283

Level 2 upgrade

804262 Chassis 747 3mm Rear section less flex
http://www.serpent.com/product/804262

804273 Chassis weight 25gr 747 Play with weight balance
http://www.serpent.com/product/804273

804271 Radioplate support alu 747 Less flex
http://www.serpent.com/product/804271

Level 3 upgrade
804277 Shock bracket carbon L+R RR Tuning option
http://www.serpent.com/product/804277

804278 Anti-rollbar bracket carbon RR (2) Tuning option
http://www.serpent.com/product/804278

804284 Wheelhexagon -1mm (2) Tuning option
http://www.serpent.com/product/804284

804294 Wishbone 747 RR LW hard (2) High traction track
http://www.serpent.com/product/804294

804295 Bumperplate carbon 747 Light and looks
http://www.serpent.com/product/804295

More 747 parts may fit, but require many parts, which makes buying a complete 747 kit more likely
http://www.serpent.com/product/804005

Team Serpent