Wow Man! Looks like tyres are as expensive as onions these days!
(I just wanted to say that!

)
I bought a set of 4 X 215/75 R15 Apollo Hawkz for 18K, just a couple of months back.
I think you misunderstood the concept of upsizing. The basic idea is to keep the "rolling diameter" (total diameter of rim + tyre) of the wheels the same, only changing the proportion of the rim and the tyre. The diameter of the "rim" does increase by an inch, but this is equally compensated by a reduction in the sidewall of the tyre to maintain the overall proportion, with just a +/- 1-2% change.
Try the tyre size calculator on this page to find the best result:
Car Bibles : The Wheel and Tyre Bible Page 3 of 4
Bottomline: This will NOT overload your engine in any way.
Beyond that, it's your call.
For the alloys, do take care to check the offset, make sure they do not bulge out from the vehicle too much (a little is okay).
The headlight + front blinker assembly of the NA Sierra has those black surrounds, which probably require a different type of mount. I think that is the reason why the Sierra Turbo/Estate lights don't fit.
I might be interested in picking those lights off you, as mine have turned a bit dull. What do you mean by "a completely new set of Sierra turbo lights"? Does it include all external lights on the Sierra Turbo? Do get it with you the day we meet.
For the Victa ORVMs, I think a bit of tinkering is required, but it's well worth the effort, considering the snail's pace at which the power window rolls down every time you have to adjust the stock ORVM. Not to mention water entering in the rainy season.
For the guages, I think your best bet is to fit a completely new console. Check if you can use the Victa IDI's console, since the meters will probably be compatible with the Sierra.
I have "reserved" this weekend for the Mumbai trip. Right now I have this severe respiratory infection, am currently on antibiotics. In all probability, it will be gone before the weekend, fingers crossed.
Vaze Buwa, Kamat Sir, are we on for this weekend?
- Bullitt.