I'm taking over an incomplete Locost 7 build.
Originally set up for Mazzzzdaaa, yech!
So, I have a choice of engine upgrades available.
Warmed up Buick 231 and four speed, NOS (Zero miles) carbed Buick Turbo from the 80's with four speed (Will it fit under the bonnet?), and Buick 215 V8 with VERY hot 11-1 pistons, road race cam etc. All run surprisingly close for cost. The warmed up 231 is an engine I already have that was intended for a different build, so less out of pocket at this time.
The cheapest but more complicated and lighter path would be a Suzuki 1.6 16V. They can be found and rebuilt very cheaply but suffer from fuel-infection and ECM headaches. I'm not much of a fan of Japanese engines but the Suzi's are aluminum block and head with SOHC and around 100 HP which should be fun, but not a killer of inexperienced drivers.
The main factor to drive the decision is "What would sell best-most $ once completed"?
Suzy and five speed are simple, five speed can be added to the Buick's but drives cost up.
Not certain what the retail value of a nicely done Locost 7 is these days, I expect engine choice influences that fairly heavily.
Reasoned suggestions that do not involve LS!, Ford, Honda, Miata will be appreciated.