Well like said the 1.7 engine is just plug and play. Fast Ford mag did a feature on fitting a puma engine to a fiesta. I dont know if its still on the ff web site but it used to be.
I think a 4 branch manifold can be had for about 150 quid. This will defo free up the engine.
What power is the 1.6?? The 1.7s are about 125bhp. Mine used to keep up with ST170s in first and second gear.
I did my puma on the cheap too. I bought a set of cheapy bucket seats for 100 quid then won a complete interior for 10 quid. I used the front seat mounts and bolted them to some strips of metal then bolted the bucket seats to the metal.