Hi!
As said, discs are great, but a wide 5 conversion is a few bob to spend, or change the lot to later bay discs, hubs etc, but would need a change of wheels, or as mentioned, properly go through the og drum set up and rebuild and replace, they work quite well, you have to press (hard!) as you are not running a servo either, you have the same set up as my bus, and my brakes are fine, not pulling either direction when braking hard, though a little "pulsing" on the pedal, so one or more of the drums is a little oval maybe. But I am sure you may be able to get a og set skimmed a little maybe?
I have locked up my brakes before - but was pressing really hard - it was either the narrow bridge or the lorry, and i didn't fancy either :shock:
My bus is stock, but if you have a tuned engine, or just drive quite fast, than maybe a disc and servo set up may give a little more re-assurance? But as already said, if it is all new and sorted well a drum set up isn't too bad - you could always retro fit a remote servo to aid the pedal pressure, it won't increase the performance, but you wont have to press quite so hard!
At least that way, you are keeping it og, but there are quite a few options out there, sorting the drums proper is the cheapest! You may well find, they just need adjusting - they do every so often - unlike a disc setup, that's one advantage, probably less prone to overheating than drums, but hey! How fast do you wanna go with only 40-50 bhp?
Cheers!
Alistair