if you use a sierra 1800 block you need to modify the sump to clear the downpipe or fit the 1.6 cvh sump with a bit of fiddling. you put the 1.6 head on and if you fit 1800 zetec pistons you can get some good power out of one. ferriday engineering used to do these conversions and with a 34 dmtr carb, kent 22 cam and a bit of porting 140bhp can be had and with twin 40s anything from 150 to 160bhp then even more with a more aggressive cam and larger valves etc