Ashley have their faults, but i wouldnt dismiss them out of hand.
Just remember that the most important tools for fitting them are a hammer and a crowbar, as their spacings can be a little....creative.
On the plus side, they are very reasonable - and the ones ive used (sierra, Fiesta MkI and Cortina MkV) have all served me well. Spencer Ashley (MPC) is also an extremely affable chap and willing to help.
Theres also a I4 manifold developed already, sorted out by the FSOC..and although its for a sierra, im sure it can be adapted quite easily