Story is that the car has being converted back to original road car spec.
One good source of info of Lotus Esprit chassis raced is : https://www.racingsportscars.com/type/Lotus/Esprit.html
Basically what I found of early Esprits there were 2 cars build for Fia (DRM) races build along the lines of Group 5 regulations.
1 is the "Jenvey" car which is rebuild and running historics. And one is in the USA. (And for sale, please let me know if you are interested) Both are Lotus esprit bodies over a space frame chassis. The USA car got a bit more original Lotus left in it. Rear suspension is modified to some formula spec and engine a Ford DBA. To run them competitively they need over 300 Hp for sure.
Other cars build are the Turbo as you pictured, this was for UK club level racing only. And very close to a original car. There was also a "Paul Matty" hillclimb car. Which was a spaceframe, without any Esprit bits. And there were various thundersaloon/modsport/special GT chassis made. Basically also spaceframe without any real esprit bits. (The AET car was re-bodied with a Skoda body) Some are for sale though for cheap:
Also there was a black Esprit for sale a while ago in the UK. Not sure if it was a modsport or Group 5. Looked a lot better than the current for sale items.
And the S1/S2 car which ought to have run Daytona in 1981 was for sale in the USA some years ago. Not sure what happend to it.
To get something with a HTP you either need to build something along the lines of a Group 5 car. Maybe the for sale modsport cars can be a good base. Or build a Group 4 along the Fia https://historicdb.fia.com/car/lotus-esprit regulations. But not sure if there was ever a Lotus Esprit in a official Fia group 4 race.
My car was a USA SCCA car which was build along the lines of Group 4 regulations but raced club level in the USA. So if you need any details for inspiration please let me know.