The later generation Mk3's had round fluid filled mounts so a 1jz will bolt up to them. However I don't know if everything else is in the right spot under the bonnet. I did an early non-turbo MA70 to 1jz-gte conversion using a JZA-70 front cut and had to use the power steering and engine fan reseviours from the JZA-70 because they were in the wrong spot. Many little things like this were different from the MA to the JZA, and the front cut was essential. The manual front cut was very hard to find and cost more than an auto. I was going from manual to manual so this bit was easy. But the clutch master cylinder from the JZA was required. JZA-70's did come in a targa-top. However they are rumoured to not be as strong as the hardtop. The 1jz motor is pretty quick. Despite the effort involved it was all worthwhile........
LOL - "I can unbolt one and bolt in the other" - it all sounds so easy...