You can run a .28 in a truggy There are loads of engines suitable but its all down to price, RB's are awesome, reliable and fast but there pretty expensive if you want one with enough grunt. AXE have just released the .25 truggy engine which looks to be good but not seen any user reviews of it yet...
As for .28's, well theres the Go .28, OS .28 (Amazing engine!), and many more out there, im sure you wouldnt go far wrong with either of them 28's.
For club level you wont need an EFRA legal pipe, you can use what you wish
EDIT: Just looked in my BRCA Handbook. It seems that you must use a .21 for all classes, at my club they allow .21's in buggies and up to .28 in truggies so thats where the confusion came from :/
Quoted from BRCA Manual