I would call it a modded Deluxe Powerhouse.

I agree, call it what it is, what you called it to begin with, a partscaster. That is unless you are trying to fool someone by claiming "Clapton Spec" which it is not. The MIM parts may be close, but let's not try to kid anyone here, Clapton didn't spec this one, nor are the parts the same specs as a Clapton Strat. You can get much closer to a "Clapton Strat" using MIA parts, not imitations.

To me, it is irritating, to say the least, when someone plays around with the name of a guitar to make it appear to be something it's not. And there is nothing at all "Clapton" about a partscaster. It sounds like a fine guitar, I don't think you can get $500 though for a MIM partscaster. If none of the parts came from an actual Clapton Strat, then his name should not be used in your ad, it would be deceitful.

Maybe a "Custom Modified Powerhouse Strat".

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.

Now this is getting interesting! The first guitar in my signature is my beloved '91 MiM Standard, evolved over many years to have proper body routing, VN's (now changed to Laces), mid-boost etc. I regard it as having 'Clapton' electrics as this is what I, and many others who do this, are trying to emmulate.
It isn't a Clapton Strat, I wouldn't try to sell it as one (not selling it anyway), but as this is what it is directly modelled on, how can it be best described?

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Standard Stratocaster w/mid-boost & Lace Sensors
Am. Standard Stratocaster FSR Daphne Blue
Tele-bration Mahogany Telecaster
Fender Pro Junior w/custom 2x10 tweed cab - nice!
Koch Twintone 2
The odd Parker and PRS

I would advertise as,
Clapton-inspired parts Stratocaster, a monster upgrade to an affordable guitar.

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FIGHT!