If you already have variable length chromosomes, then it shouldnt matter how you do it, you just need to select a crossover point for each of them, and then crossover as normal.
For example using your chromosomes, I have selected two points (.) at random:
1 6 8 9.0 3 4 7 5
3 6.5 7 8 5
With resulting chromosomes:
1 6 8 9.5 7 8 5
3 6.0 3 4 7 5