77celica engine swap

I want to get ridd of 20R in my 77 Celica GT RA29. It has the five speed, i assume its a W##(not exactly sure). I'd like an engine that will use the original transmission, with a modified bellhousing, which i should be able to get from Toysport. 4 cylinder's i've considered are 3t-gte, but really unavailable, and 3sgte, but that would require custom intake and exhaust manifolds. I'm open to 6's possibly 1g-gte, 1jz-gte, toysport told me 7m-gte, but i've heard of many head problems. I guess the 2jzgte is an option, please just tell me if that's just too rediculous. I've seen some lexus v-8 pics from australia, but toysport told me lexus v-8's are weak. What about that 300hp 1uz with variable valve timing from the 98up GS 400? If you have any technical information or suggestions please give them. I really would like to see projects that have previously been completed successfully. I really need feedback on the options i gave, i am serious about doing this project this winter. I've heard that the 79 supra rear end with disks and limited slip will fit in the car, hoping that it would handle good power. HOw much can that transmission i have realistically handle. I'm glad the engine bay is long and large on the hatchback. I more concern is balance, i need to know the weight of those 6's and v8 so i don't create some ill handling car.
Sorry to go on so long, but i wanted to be specific.
Please help!
Will

Well I wouldn't listen to anyone who told you the lexus/toyota V8 was weak.
Its a great engine, extremely light, compact, and very powerful. Its so good its become the new darling of the hot rod scene, and there is a huge wealth of aftermarket parts now avliable for it.

If you manage to find a 3t then its deffintly the motor of choice, I actualy know where one is, unforunatly its on the other side of the world to you.

I didnt know a 6cly would fit in the 77 celica though, the US model must be quite a bit more differnt than I thought.
But it will definitly mess up the cars balance, its a lot of extra weight to put over the front wheels.
You will be able to fix it with new springs and shocks, but it may take some effort to get the right balance, and at the end of the day with all that extra interia there will be more understeer and less response at turn in.