Again, Welcome to the forum
I like your idea, one day I want to build an electric Huayra looking car.
There are two kits around for your Aventador. Nate made his own CNC kit and a Mexico kit was made using a wood buck. The kits are not the same size; one is just ¾ of an inch shorter. Either way – that’s what’s out there so that’s what will be replicated for a long time to come.
Think of your donor first in terms of weight, size, safety, interior, options, etc.
What we continue seeing is replicas that look shiny but are a headache to operate. People keep on selling them to one another after owning them for less than a year. So, if you don’t want anti lock brakes, power steering, coil overs, air condition, etc. then you can use just about any older car but your car will not be a joy to drive.
So to answer your question, Yes; you should start on the frame before worrying about the fiberglass body.
The answer to your second question is No, you should not in theory stretch the car if it’s not complete an running already as an electric car. For several reasons, I will mention two of them here
1) you want to be able to register the car as electric before the kit installation because it will be almost impossible to get it approved via inspection after the body work.
2) You want to start with an operating roller so once you stretch it you know what to go back to in terms of putting the drive train components together as you had started.
Just assume that you will have 12” of extra space added onto the length of the car and use that in your calculations; that’s the only variant. You do not need the kit to figure out the battery configuration as you'd come to see that there is so much space.
SPENDING
You can spend $20K on the electric conversion depending on your preference of power.
However, for the replica YOU WILL SPEND MORE.
The Aventador has many grills/lights and other things on the exterior that will cost a lot. The 16 OEM grill set on my LP640 cost me $2k in total so I could see ur grill set costing you a lot more. Just an idea there..
Then I do not know what your interior idea is like…
I also want to warn you that the Aventador is a really large car
Again, for your donor you should think of the options especially comfort and interior variants. The Vast majority of the 40 lambo builds on this forum had to go through creating a new interior and adding some non-oem components to the donors’ option to have a pleasant experience. So, think of that as well…
Can you keep it operational while you work on it? In theory Yes.
You need a windshield, lights, and the car to be cohesive to keep the car on the road. If you install such items then you are okay to drive it but why would you want to drive it in such shape? The issue will be that you don’t have lights and a windshield for your aventador. So in practice NO.
It took me 6 weeks from the day I drove my MR2 one last time till the day I placed a kit on it and drove it around the block with the Murci Shell on.
Knowing what I know now, I could have mounted the body onto the car via a frame I prefabricate and then plug in my lights and glue my windshield on and drive the car within a week – but again, I had to design all that; and that took me weeks. There is so much for what’s under the skit of a replica (: it’s fun but get ready for a crazy ride.
If it were me, I would 1 buy a donor, 2 turn in into an electric car, 3 change the title to electric at dmv, and 4 drive it around for a while. If i am satisfied until that point then I will start thinking about making it an aventador.
That's my 2c
