If ya don't mind loud, then forget the exhaust, have the manifold
going into a bit of flexible gas flue (tubule dryer stuff, made in
metal), then along under the sills, a bit of wire mesh for the
silencer to get it passed the MOT. And bobs your uncle you have
an exhaust system to scare boy racers with.
Alternatively you could put on an extractor manifold which will
bump up the power allot.
Or. You could hack at your standard exhaust with an electric drill,
and make it multi ported. You could put a spark plug in the
end, and connect it to the ignition system, so that you can light
farts if you know what I mean.
Or, you could run hoses to ya carburettor ports, and forget the
Make a sheet metal copy of the manifold plate, and weld some tubes
to it, and shove them out the sides, going through slightly bigger
peace's of tubes as "silencers" tuned to get a nice low note. So you
will have four exhausts.
You could have fun doing some DIY here.
Yellow '79 spit wired by a trained marmot