The Lseries is a pretty easy conversion though it requires a modified cross member gearbox cross member and Sump amongst a few other little things. The biggest part is engineering it Cost wise. Because funnily its cheaper to buy an L16 or L18 and 5 speed than it is to buy an A14 Or A15 with 5 speed. You could look around and most likely pick up a rusty old stanza or 200B with all the running gear and theres most ya bits for a conversion. Also a L16 or L18 with good compression extractors and a weber would nearly see you blow off a slightly worked A14 or A15. and still have a reliable economical car. Just to add any work you did to the L series engine would increase your power larger than an A series with more work Just because of power to weight ratio. Also look into modified cars because you may not be able to have them if your not allowed V8's and Turbos.