My advice to you is to have a look at one before you do anything else. You need to make sure that you have enough room under the bonnet. Not only height wise but also width wise.
My kit had to be modified to fit it in. The result being narrower footwells. Not by much but enough to notice.
These motors also only comply to ADR27. Not the current standard.
When you say security, what do you mean?
Price varies on these motors. Your best bet would be to buy a Japanese Toyota Crown front half cut. Motor is the same as the Lexus. That way you get the complete setup ie: ECU.,wiring loom. air flow meter etc. I made the mistake of buying a motor only and I ended up spending a lot more to get everything needed to run it.
There are a number of places around that specialise in these motors. They modify the standard loom and return it to you with 5 wires exposed. Very simple then to hook up.
www.quickfitmotorsport.com.au
I am in the final stages of getting mine supercharged. Nothing needs to be done internally due to the motor being extremely over engineered.