Getting the 1JZ first up is worth it over the 7M if you are doing a conversion. You get a newer design engine (which hopefully has done less Kms), which pays off with reliability (i.e. head gaskets etc). It is also a better performance baseline to build on if you come into megabucks.
I know you are saving for a house, but now you know the sweeeet sweeet pain of all car junkies! Not enough Dosh!