I have 2 friends that did ~500whp and 450wtq stock internals for ages (one sold his car, and the other is putting his motor into another car). using that level of power as a comparison is a joke..
1Js do this all day everyday here, Japan, Aussyland, UK, and tracks across the globe. It will always cost money, but it's not too hard to achieve.
Motor choice is always about what you want to do, not about others. Opinions are great, but they're like kittens, everyone's always giving them away. Most of the 1J owners that have read this thread are probably not saying anything because they know if they do, it will do little to solve or convince anyone of anything. So often the fact that it's a 2.5L is criticized for not having enough power (whp, wtq, power under the curve). I can however tell you this, there are plenty of cars like those listed above that will tear you a new ass if you do not respect them. The 1J easily keeps up with the 7M or 2J to a certain point, and folks really need to realize this or just escape reality all together.
The important piece: like others have said correctly, these days it no longer makes a whole lot of sense. The 2J is the same price, and JZA70 front-clips are near unheard of anymore for a variety of reasons. On the other hand, the 7M was a great motor for it's time and still can be with a lot of hardwork and patience, but it comes down to how much catch-up and fix this design flaw here and there you end up wanting to play. At the same time, at least one already has the motor and doesn't have to swap and so forth.