depends on what you concider high hp the 25 can handle around 550hp and be fine the 26 is in the 2jz area they are known for 550-700 hp stock bottom ends. others will swear up and down on the AUS and NZ sites that they can handle more, but I am not sure. I mean they are underrated stock, mine bone stock everything put down 309 rwhp on stock boost, stock rb25clutch, stock sidemount, stock everything, except for air filters.
If your looking into conquest ect I will be honest they lack suspension aftermarket, and if you are looking into doing all this yourself, sounds like a huge price tag. If you can do all the fab work yourself then you should be fine, but I bet you will be in the 20k-25k price range before the car even touches a road. I like the conquest for looks thats as far as it goes. If you are looking for another chassis trylooking for mint 240's s13's-s14;s they are still cheap and have much more aftermarket support, and there are plenty of lsx 240's already running around.