go for the mini, sounds like a great buy, I currently have a mini which is (currently) pretty stock. Minis are the #### for handling they are awesome, already low with hard suspension. If you want a fun club racer for not much money minis are the way. To start developing power for not much cost this is what you need to do: get a 1300 (big valve) engine from an MG1300 of bore the origional engine to that size, get a hot cam, port the head, add extractors, put a twin carb manifold with twin choke side draft webbers. all relatively cheap mods and you develop about 90-110 HP. with wide-wheels and 4 wheel discs it should be a force to reckon with. However if you were to do the same modifications to you datsun you would definently davelop more power. The choice is really yours.